friendlier error messages when invoke/lessc are missing

and not needed.

IPython/html/tasks.py

@@ -1,83 +1,108 b''
 """invoke task file to build CSS"""
 
-from invoke import task, run
+from __future__ import print_function
+
 import os
+import sys
 from distutils.version import LooseVersion as V
 from subprocess import check_output
 
+from invoke import task, run
+from invoke.runner import Result
+from invoke.exceptions import Failure
+
 pjoin = os.path.join
 static_dir = 'static'
 components_dir = pjoin(static_dir, 'components')
 here = os.path.dirname(__file__)
 
 min_less_version = '2.0'
 max_less_version = '3.0' # exclusive if string
 
+
+def _fail(msg=''):
+    """Fail a task, logging a message to stderr
+    
+    raises a special Failure Exception from invoke.
+    """
+    if msg:
+        print(msg, file=sys.stderr)
+    # raising a Failure allows us to avoid a traceback
+    # we only care about exited, but stdout, stderr, pty are required args
+    raise Failure(Result(stdout='', stderr='', pty=False, exited=1))
+
 def _need_css_update():
     """Does less need to run?"""
     
     static_path = pjoin(here, static_dir)
     css_targets = [ 
         pjoin(static_path, 'style', '%s.min.css' % name)
         for name in ('style', 'ipython')
     ]
     css_maps = [t + '.map' for t in css_targets]
     targets = css_targets + css_maps
     if not all(os.path.exists(t) for t in targets):
         # some generated files don't exist
         return True
     earliest_target = sorted(os.stat(t).st_mtime for t in targets)[0]
     
     # check if any .less files are newer than the generated targets
     for (dirpath, dirnames, filenames) in os.walk(static_path):
         for f in filenames:
             if f.endswith('.less'):
                 path = pjoin(static_path, dirpath, f)
                 timestamp = os.stat(path).st_mtime
                 if timestamp > earliest_target:
                     return True
     
     return False
 
 @task
 def css(minify=False, verbose=False, force=False):
     """generate the css from less files"""
     # minify implies force because it's not the default behavior
     if not force and not minify and not _need_css_update():
         print("css up-to-date")
         return
     
     for name in ('style', 'ipython'):
         source = pjoin('style', "%s.less" % name)
         target = pjoin('style', "%s.min.css" % name)
         sourcemap = pjoin('style', "%s.min.css.map" % name)
         _compile_less(source, target, sourcemap, minify, verbose)
 
+
 def _compile_less(source, target, sourcemap, minify=True, verbose=False):
     """Compile a less file by source and target relative to static_dir"""
     min_flag = '-x' if minify else ''
     ver_flag = '--verbose' if verbose else ''
     
+    install = "(npm install -g 'less@<{}')".format(max_less_version)
     # pin less to version number from above
     try:
         out = check_output(['lessc', '--version'])
     except OSError as err:
-        raise ValueError("Unable to find lessc.  Please install lessc >= %s and < %s " \
-                         % (min_less_version, max_less_version))
+        _fail("Unable to find lessc.  Rebuilding css requires less >= {0} and < {1} {2}".format(
+            min_less_version, max_less_version, install
+        ))
     out = out.decode('utf8', 'replace')
     less_version = out.split()[1]
     if min_less_version and V(less_version) < V(min_less_version):
-        raise ValueError("lessc too old: %s < %s. Use `$ npm install less@X.Y.Z` to install a specific version of less" % (less_version, min_less_version))
+        _fail("lessc too old: {} < {} {}".format(
+            less_version, min_less_version, install,
+        ))
     if max_less_version and V(less_version) >= V(max_less_version):
-        raise ValueError("lessc too new: %s >= %s. Use `$ npm install less@X.Y.Z` to install a specific version of less" % (less_version, max_less_version))
+        _fail("lessc too new: {} >= {} {}".format(
+            less_version, max_less_version, install,
+        ))
     
     static_path = pjoin(here, static_dir)
     cwd = os.getcwd()
     try:
         os.chdir(static_dir)
         run('lessc {min_flag} {ver_flag} --source-map={sourcemap} --source-map-basepath={static_path} --source-map-rootpath="../" {source} {target}'.format(**locals()),
             echo=True,
         )
     finally:
         os.chdir(cwd)
 

setupbase.py

@@ -1,755 +1,765 b''
 # encoding: utf-8
 """
 This module defines the things that are used in setup.py for building IPython
 
 This includes:
 
     * The basic arguments to setup
     * Functions for finding things like packages, package data, etc.
     * A function for checking dependencies.
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 from __future__ import print_function
 
 import errno
 import os
 import sys
 
 from distutils import log
 from distutils.command.build_py import build_py
 from distutils.command.build_scripts import build_scripts
 from distutils.command.install import install
 from distutils.command.install_scripts import install_scripts
 from distutils.cmd import Command
+from distutils.errors import DistutilsExecError
 from fnmatch import fnmatch
 from glob import glob
-from subprocess import check_call
+from subprocess import Popen, PIPE
 
 from setupext import install_data_ext
 
 #-------------------------------------------------------------------------------
 # Useful globals and utility functions
 #-------------------------------------------------------------------------------
 
 # A few handy globals
 isfile = os.path.isfile
 pjoin = os.path.join
 repo_root = os.path.dirname(os.path.abspath(__file__))
 
 def oscmd(s):
     print(">", s)
     os.system(s)
 
 # Py3 compatibility hacks, without assuming IPython itself is installed with
 # the full py3compat machinery.
 
 try:
     execfile
 except NameError:
     def execfile(fname, globs, locs=None):
         locs = locs or globs
         exec(compile(open(fname).read(), fname, "exec"), globs, locs)
 
 # A little utility we'll need below, since glob() does NOT allow you to do
 # exclusion on multiple endings!
 def file_doesnt_endwith(test,endings):
     """Return true if test is a file and its name does NOT end with any
     of the strings listed in endings."""
     if not isfile(test):
         return False
     for e in endings:
         if test.endswith(e):
             return False
     return True
 
 #---------------------------------------------------------------------------
 # Basic project information
 #---------------------------------------------------------------------------
 
 # release.py contains version, authors, license, url, keywords, etc.
 execfile(pjoin(repo_root, 'IPython','core','release.py'), globals())
 
 # Create a dict with the basic information
 # This dict is eventually passed to setup after additional keys are added.
 setup_args = dict(
       name             = name,
       version          = version,
       description      = description,
       long_description = long_description,
       author           = author,
       author_email     = author_email,
       url              = url,
       download_url     = download_url,
       license          = license,
       platforms        = platforms,
       keywords         = keywords,
       classifiers      = classifiers,
       cmdclass         = {'install_data': install_data_ext},
       )
 
 
 #---------------------------------------------------------------------------
 # Find packages
 #---------------------------------------------------------------------------
 
 def find_packages():
     """
     Find all of IPython's packages.
     """
     excludes = ['deathrow', 'quarantine']
     packages = []
     for dir,subdirs,files in os.walk('IPython'):
         package = dir.replace(os.path.sep, '.')
         if any(package.startswith('IPython.'+exc) for exc in excludes):
             # package is to be excluded (e.g. deathrow)
             continue
         if '__init__.py' not in files:
             # not a package
             continue
         packages.append(package)
     return packages
 
 #---------------------------------------------------------------------------
 # Find package data
 #---------------------------------------------------------------------------
 
 def find_package_data():
     """
     Find IPython's package_data.
     """
     # This is not enough for these things to appear in an sdist.
     # We need to muck with the MANIFEST to get this to work
     
     # exclude components and less from the walk;
     # we will build the components separately
     excludes = [
         pjoin('static', 'components'),
         pjoin('static', '*', 'less'),
     ]
     
     # walk notebook resources:
     cwd = os.getcwd()
     os.chdir(os.path.join('IPython', 'html'))
     static_data = []
     for parent, dirs, files in os.walk('static'):
         if any(fnmatch(parent, pat) for pat in excludes):
             # prevent descending into subdirs
             dirs[:] = []
             continue
         for f in files:
             static_data.append(pjoin(parent, f))
     
     components = pjoin("static", "components")
     # select the components we actually need to install
     # (there are lots of resources we bundle for sdist-reasons that we don't actually use)
     static_data.extend([
         pjoin(components, "backbone", "backbone-min.js"),
         pjoin(components, "bootstrap", "js", "bootstrap.min.js"),
         pjoin(components, "bootstrap-tour", "build", "css", "bootstrap-tour.min.css"),
         pjoin(components, "bootstrap-tour", "build", "js", "bootstrap-tour.min.js"),
         pjoin(components, "es6-promise", "*.js"),
         pjoin(components, "font-awesome", "fonts", "*.*"),
         pjoin(components, "google-caja", "html-css-sanitizer-minified.js"),
         pjoin(components, "jquery", "jquery.min.js"),
         pjoin(components, "jquery-ui", "ui", "minified", "jquery-ui.min.js"),
         pjoin(components, "jquery-ui", "themes", "smoothness", "jquery-ui.min.css"),
         pjoin(components, "jquery-ui", "themes", "smoothness", "images", "*"),
         pjoin(components, "marked", "lib", "marked.js"),
         pjoin(components, "requirejs", "require.js"),
         pjoin(components, "underscore", "underscore-min.js"),
         pjoin(components, "moment", "moment.js"),
         pjoin(components, "moment", "min", "moment.min.js"),
         pjoin(components, "term.js", "src", "term.js"),
         pjoin(components, "text-encoding", "lib", "encoding.js"),
     ])
     
     # Ship all of Codemirror's CSS and JS
     for parent, dirs, files in os.walk(pjoin(components, 'codemirror')):
         for f in files:
             if f.endswith(('.js', '.css')):
                 static_data.append(pjoin(parent, f))
     
     os.chdir(os.path.join('tests',))
     js_tests = glob('*.js') + glob('*/*.js')
 
     os.chdir(os.path.join(cwd, 'IPython', 'nbconvert'))
     nbconvert_templates = [os.path.join(dirpath, '*.*')
                             for dirpath, _, _ in os.walk('templates')]
 
     os.chdir(cwd)
 
     package_data = {
         'IPython.config.profile' : ['README*', '*/*.py'],
         'IPython.core.tests' : ['*.png', '*.jpg'],
         'IPython.lib.tests' : ['*.wav'],
         'IPython.testing.plugin' : ['*.txt'],
         'IPython.html' : ['templates/*'] + static_data,
         'IPython.html.tests' : js_tests,
         'IPython.qt.console' : ['resources/icon/*.svg'],
         'IPython.nbconvert' : nbconvert_templates +
             [
                 'tests/files/*.*',
                 'exporters/tests/files/*.*',
                 'preprocessors/tests/files/*.*',
             ],
         'IPython.nbconvert.filters' : ['marked.js'],
         'IPython.nbformat' : [
             'tests/*.ipynb',
             'v3/nbformat.v3.schema.json',
             'v4/nbformat.v4.schema.json',
             ],
         'IPython.kernel': ['resources/*.*'],
     }
     
     return package_data
 
 
 def check_package_data(package_data):
     """verify that package_data globs make sense"""
     print("checking package data")
     for pkg, data in package_data.items():
         pkg_root = pjoin(*pkg.split('.'))
         for d in data:
             path = pjoin(pkg_root, d)
             if '*' in path:
                 assert len(glob(path)) > 0, "No files match pattern %s" % path
             else:
                 assert os.path.exists(path), "Missing package data: %s" % path
 
 
 def check_package_data_first(command):
     """decorator for checking package_data before running a given command
     
     Probably only needs to wrap build_py
     """
     class DecoratedCommand(command):
         def run(self):
             check_package_data(self.package_data)
             command.run(self)
     return DecoratedCommand
 
 
 #---------------------------------------------------------------------------
 # Find data files
 #---------------------------------------------------------------------------
 
 def make_dir_struct(tag,base,out_base):
     """Make the directory structure of all files below a starting dir.
 
     This is just a convenience routine to help build a nested directory
     hierarchy because distutils is too stupid to do this by itself.
 
     XXX - this needs a proper docstring!
     """
 
     # we'll use these a lot below
     lbase = len(base)
     pathsep = os.path.sep
     lpathsep = len(pathsep)
 
     out = []
     for (dirpath,dirnames,filenames) in os.walk(base):
         # we need to strip out the dirpath from the base to map it to the
         # output (installation) path.  This requires possibly stripping the
         # path separator, because otherwise pjoin will not work correctly
         # (pjoin('foo/','/bar') returns '/bar').
 
         dp_eff = dirpath[lbase:]
         if dp_eff.startswith(pathsep):
             dp_eff = dp_eff[lpathsep:]
         # The output path must be anchored at the out_base marker
         out_path = pjoin(out_base,dp_eff)
         # Now we can generate the final filenames. Since os.walk only produces
         # filenames, we must join back with the dirpath to get full valid file
         # paths:
         pfiles = [pjoin(dirpath,f) for f in filenames]
         # Finally, generate the entry we need, which is a pari of (output
         # path, files) for use as a data_files parameter in install_data.
         out.append((out_path, pfiles))
 
     return out
 
 
 def find_data_files():
     """
     Find IPython's data_files.
 
     Just man pages at this point.
     """
 
     manpagebase = pjoin('share', 'man', 'man1')
 
     # Simple file lists can be made by hand
     manpages = [f for f in glob(pjoin('docs','man','*.1.gz')) if isfile(f)]
     if not manpages:
         # When running from a source tree, the manpages aren't gzipped
         manpages = [f for f in glob(pjoin('docs','man','*.1')) if isfile(f)]
 
     # And assemble the entire output list
     data_files = [ (manpagebase, manpages) ]
 
     return data_files
 
 
 def make_man_update_target(manpage):
     """Return a target_update-compliant tuple for the given manpage.
 
     Parameters
     ----------
     manpage : string
       Name of the manpage, must include the section number (trailing number).
 
     Example
     -------
 
     >>> make_man_update_target('ipython.1') #doctest: +NORMALIZE_WHITESPACE
     ('docs/man/ipython.1.gz',
      ['docs/man/ipython.1'],
      'cd docs/man && gzip -9c ipython.1 > ipython.1.gz')
     """
     man_dir = pjoin('docs', 'man')
     manpage_gz = manpage + '.gz'
     manpath = pjoin(man_dir, manpage)
     manpath_gz = pjoin(man_dir, manpage_gz)
     gz_cmd = ( "cd %(man_dir)s && gzip -9c %(manpage)s > %(manpage_gz)s" %
                locals() )
     return (manpath_gz, [manpath], gz_cmd)
 
 # The two functions below are copied from IPython.utils.path, so we don't need
 # to import IPython during setup, which fails on Python 3.
 
 def target_outdated(target,deps):
     """Determine whether a target is out of date.
 
     target_outdated(target,deps) -> 1/0
 
     deps: list of filenames which MUST exist.
     target: single filename which may or may not exist.
 
     If target doesn't exist or is older than any file listed in deps, return
     true, otherwise return false.
     """
     try:
         target_time = os.path.getmtime(target)
     except os.error:
         return 1
     for dep in deps:
         dep_time = os.path.getmtime(dep)
         if dep_time > target_time:
             #print "For target",target,"Dep failed:",dep # dbg
             #print "times (dep,tar):",dep_time,target_time # dbg
             return 1
     return 0
 
 
 def target_update(target,deps,cmd):
     """Update a target with a given command given a list of dependencies.
 
     target_update(target,deps,cmd) -> runs cmd if target is outdated.
 
     This is just a wrapper around target_outdated() which calls the given
     command if target is outdated."""
 
     if target_outdated(target,deps):
         os.system(cmd)
 
 #---------------------------------------------------------------------------
 # Find scripts
 #---------------------------------------------------------------------------
 
 def find_entry_points():
     """Defines the command line entry points for IPython
 
     This always uses setuptools-style entry points. When setuptools is not in
     use, our own build_scripts_entrypt class below parses these and builds
     command line scripts.
 
     Each of our entry points gets both a plain name, e.g. ipython, and one
     suffixed with the Python major version number, e.g. ipython3. 
     """
     ep = [
             'ipython%s = IPython:start_ipython',
             'ipcontroller%s = IPython.parallel.apps.ipcontrollerapp:launch_new_instance',
             'ipengine%s = IPython.parallel.apps.ipengineapp:launch_new_instance',
             'ipcluster%s = IPython.parallel.apps.ipclusterapp:launch_new_instance',
             'iptest%s = IPython.testing.iptestcontroller:main',
         ]
     suffix = str(sys.version_info[0])
     return [e % '' for e in ep] + [e % suffix for e in ep]
 
 script_src = """#!{executable}
 # This script was automatically generated by setup.py
 if __name__ == '__main__':
     from {mod} import {func}
     {func}()
 """
 
 class build_scripts_entrypt(build_scripts):
     """Build the command line scripts
     
     Parse setuptools style entry points and write simple scripts to run the
     target functions.
     
     On Windows, this also creates .cmd wrappers for the scripts so that you can
     easily launch them from a command line.
     """
     def run(self):
         self.mkpath(self.build_dir)
         outfiles = []
         for script in find_entry_points():
             name, entrypt = script.split('=')
             name = name.strip()
             entrypt = entrypt.strip()
             outfile = os.path.join(self.build_dir, name)
             outfiles.append(outfile)
             print('Writing script to', outfile)
 
             mod, func = entrypt.split(':')
             with open(outfile, 'w') as f:
                 f.write(script_src.format(executable=sys.executable,
                                           mod=mod, func=func))
             
             if sys.platform == 'win32':
                 # Write .cmd wrappers for Windows so 'ipython' etc. work at the
                 # command line
                 cmd_file = os.path.join(self.build_dir, name + '.cmd')
                 cmd = '@"{python}" "%~dp0\{script}" %*\r\n'.format(
                         python=sys.executable, script=name)
                 log.info("Writing %s wrapper script" % cmd_file)
                 with open(cmd_file, 'w') as f:
                     f.write(cmd)
 
         return outfiles, outfiles
 
 class install_lib_symlink(Command):
     user_options = [
         ('install-dir=', 'd', "directory to install to"),
         ]
 
     def initialize_options(self):
         self.install_dir = None
 
     def finalize_options(self):
         self.set_undefined_options('symlink',
                                    ('install_lib', 'install_dir'),
                                   )
 
     def run(self):
         if sys.platform == 'win32':
             raise Exception("This doesn't work on Windows.")
         pkg = os.path.join(os.getcwd(), 'IPython')
         dest = os.path.join(self.install_dir, 'IPython')
         if os.path.islink(dest):
             print('removing existing symlink at %s' % dest)
             os.unlink(dest)
         print('symlinking %s -> %s' % (pkg, dest))
         os.symlink(pkg, dest)
 
 class unsymlink(install):
     def run(self):
         dest = os.path.join(self.install_lib, 'IPython')
         if os.path.islink(dest):
             print('removing symlink at %s' % dest)
             os.unlink(dest)
         else:
             print('No symlink exists at %s' % dest)
 
 class install_symlinked(install):
     def run(self):
         if sys.platform == 'win32':
             raise Exception("This doesn't work on Windows.")
 
         # Run all sub-commands (at least those that need to be run)
         for cmd_name in self.get_sub_commands():
             self.run_command(cmd_name)
     
     # 'sub_commands': a list of commands this command might have to run to
     # get its work done.  See cmd.py for more info.
     sub_commands = [('install_lib_symlink', lambda self:True),
                     ('install_scripts_sym', lambda self:True),
                    ]
 
 class install_scripts_for_symlink(install_scripts):
     """Redefined to get options from 'symlink' instead of 'install'.
     
     I love distutils almost as much as I love setuptools.
     """
     def finalize_options(self):
         self.set_undefined_options('build', ('build_scripts', 'build_dir'))
         self.set_undefined_options('symlink',
                                    ('install_scripts', 'install_dir'),
                                    ('force', 'force'),
                                    ('skip_build', 'skip_build'),
                                   )
 
 #---------------------------------------------------------------------------
 # Verify all dependencies
 #---------------------------------------------------------------------------
 
 def check_for_dependencies():
     """Check for IPython's dependencies.
 
     This function should NOT be called if running under setuptools!
     """
     from setupext.setupext import (
         print_line, print_raw, print_status,
         check_for_sphinx, check_for_pygments,
         check_for_nose, check_for_pexpect,
         check_for_pyzmq, check_for_readline,
         check_for_jinja2, check_for_tornado
     )
     print_line()
     print_raw("BUILDING IPYTHON")
     print_status('python', sys.version)
     print_status('platform', sys.platform)
     if sys.platform == 'win32':
         print_status('Windows version', sys.getwindowsversion())
 
     print_raw("")
     print_raw("OPTIONAL DEPENDENCIES")
 
     check_for_sphinx()
     check_for_pygments()
     check_for_nose()
     if os.name == 'posix':
         check_for_pexpect()
     check_for_pyzmq()
     check_for_tornado()
     check_for_readline()
     check_for_jinja2()
 
 #---------------------------------------------------------------------------
 # VCS related
 #---------------------------------------------------------------------------
 
 # utils.submodule has checks for submodule status
 execfile(pjoin('IPython','utils','submodule.py'), globals())
 
 class UpdateSubmodules(Command):
     """Update git submodules
     
     IPython's external javascript dependencies live in a separate repo.
     """
     description = "Update git submodules"
     user_options = []
     
     def initialize_options(self):
         pass
     
     def finalize_options(self):
         pass
     
     def run(self):
         failure = False
         try:
             self.spawn('git submodule init'.split())
             self.spawn('git submodule update --recursive'.split())
         except Exception as e:
             failure = e
             print(e)
         
         if not check_submodule_status(repo_root) == 'clean':
             print("submodules could not be checked out")
             sys.exit(1)
 
 
 def git_prebuild(pkg_dir, build_cmd=build_py):
     """Return extended build or sdist command class for recording commit
     
     records git commit in IPython.utils._sysinfo.commit
     
     for use in IPython.utils.sysinfo.sys_info() calls after installation.
     
     Also ensures that submodules exist prior to running
     """
     
     class MyBuildPy(build_cmd):
         ''' Subclass to write commit data into installation tree '''
         def run(self):
             build_cmd.run(self)
             # this one will only fire for build commands
             if hasattr(self, 'build_lib'):
                 self._record_commit(self.build_lib)
         
         def make_release_tree(self, base_dir, files):
             # this one will fire for sdist
             build_cmd.make_release_tree(self, base_dir, files)
             self._record_commit(base_dir)
         
         def _record_commit(self, base_dir):
             import subprocess
             proc = subprocess.Popen('git rev-parse --short HEAD',
                                     stdout=subprocess.PIPE,
                                     stderr=subprocess.PIPE,
                                     shell=True)
             repo_commit, _ = proc.communicate()
             repo_commit = repo_commit.strip().decode("ascii")
             
             out_pth = pjoin(base_dir, pkg_dir, 'utils', '_sysinfo.py')
             if os.path.isfile(out_pth) and not repo_commit:
                 # nothing to write, don't clobber
                 return
             
             print("writing git commit '%s' to %s" % (repo_commit, out_pth))
             
             # remove to avoid overwriting original via hard link
             try:
                 os.remove(out_pth)
             except (IOError, OSError):
                 pass
             with open(out_pth, 'w') as out_file:
                 out_file.writelines([
                     '# GENERATED BY setup.py\n',
                     'commit = u"%s"\n' % repo_commit,
                 ])
     return require_submodules(MyBuildPy)
 
 
 def require_submodules(command):
     """decorator for instructing a command to check for submodules before running"""
     class DecoratedCommand(command):
         def run(self):
             if not check_submodule_status(repo_root) == 'clean':
                 print("submodules missing! Run `setup.py submodule` and try again")
                 sys.exit(1)
             command.run(self)
     return DecoratedCommand
 
 #---------------------------------------------------------------------------
 # bdist related
 #---------------------------------------------------------------------------
 
 def get_bdist_wheel():
     """Construct bdist_wheel command for building wheels
     
     Constructs py2-none-any tag, instead of py2.7-none-any
     """
     class RequiresWheel(Command):
         description = "Dummy command for missing bdist_wheel"
         user_options = []
 
         def initialize_options(self):
             pass
 
         def finalize_options(self):
             pass
 
         def run(self):
             print("bdist_wheel requires the wheel package")
             sys.exit(1)
 
     if 'setuptools' not in sys.modules:
         return RequiresWheel
     else:
         try:
             from wheel.bdist_wheel import bdist_wheel, read_pkg_info, write_pkg_info
         except ImportError:
             return RequiresWheel
         
         class bdist_wheel_tag(bdist_wheel):
 
             def add_requirements(self, metadata_path):
                 """transform platform-dependent requirements"""
                 pkg_info = read_pkg_info(metadata_path)
                 # pkg_info is an email.Message object (?!)
                 # we have to remove the unconditional 'readline' and/or 'pyreadline' entries
                 # and transform them to conditionals
                 requires = pkg_info.get_all('Requires-Dist')
                 del pkg_info['Requires-Dist']
                 def _remove_startswith(lis, prefix):
                     """like list.remove, but with startswith instead of =="""
                     found = False
                     for idx, item in enumerate(lis):
                         if item.startswith(prefix):
                             found = True
                             break
                     if found:
                         lis.pop(idx)
                 
                 for pkg in ("gnureadline", "pyreadline", "mock"):
                     _remove_startswith(requires, pkg)
                 requires.append("gnureadline; sys.platform == 'darwin' and platform.python_implementation == 'CPython'")
                 requires.append("pyreadline (>=2.0); extra == 'terminal' and sys.platform == 'win32' and platform.python_implementation == 'CPython'")
                 requires.append("pyreadline (>=2.0); extra == 'all' and sys.platform == 'win32' and platform.python_implementation == 'CPython'")
                 requires.append("mock; extra == 'test' and python_version < '3.3'")
                 for r in requires:
                     pkg_info['Requires-Dist'] = r
                 write_pkg_info(metadata_path, pkg_info)
         
         return bdist_wheel_tag
 
 #---------------------------------------------------------------------------
 # Notebook related
 #---------------------------------------------------------------------------
 
 class CompileCSS(Command):
     """Recompile Notebook CSS
     
     Regenerate the compiled CSS from LESS sources.
     
     Requires various dev dependencies, such as invoke and lessc.
     """
     description = "Recompile Notebook CSS"
     user_options = [
         ('minify', 'x', "minify CSS"),
         ('force', 'f', "force recompilation of CSS"),
     ]
     
     def initialize_options(self):
         self.minify = False
         self.force = False
     
     def finalize_options(self):
         self.minify = bool(self.minify)
         self.force = bool(self.force)
     
     def run(self):
         cmd = ['invoke', 'css']
         if self.minify:
             cmd.append('--minify')
         if self.force:
             cmd.append('--force')
-        check_call(cmd, cwd=pjoin(repo_root, "IPython", "html"))
+        try:
+            p = Popen(cmd, cwd=pjoin(repo_root, "IPython", "html"), stderr=PIPE)
+        except OSError:
+            raise DistutilsExecError("invoke is required to rebuild css (pip install invoke)")
+        out, err = p.communicate()
+        if p.returncode:
+            if sys.version_info[0] >= 3:
+                err = err.decode('utf8', 'replace')
+            raise DistutilsExecError(err.strip())
 
 
 class JavascriptVersion(Command):
     """write the javascript version to notebook javascript"""
     description = "Write IPython version to javascript"
     user_options = []
     
     def initialize_options(self):
         pass
     
     def finalize_options(self):
         pass
     
     def run(self):
         nsfile = pjoin(repo_root, "IPython", "html", "static", "base", "js", "namespace.js")
         with open(nsfile) as f:
             lines = f.readlines()
         with open(nsfile, 'w') as f:
             for line in lines:
                 if line.startswith("IPython.version"):
                     line = 'IPython.version = "{0}";\n'.format(version)
                 f.write(line)
 
 
 def css_js_prerelease(command, strict=True):
     """decorator for building js/minified css prior to a release"""
     class DecoratedCommand(command):
         def run(self):
             self.distribution.run_command('jsversion')
             css = self.distribution.get_command_obj('css')
             css.minify = True
             try:
                 self.distribution.run_command('css')
             except Exception as e:
                 if strict:
                     raise
                 else:
-                    log.warn("Failed to build css sourcemaps: %s" % e)
+                    log.warn("rebuilding css and sourcemaps failed (not a problem)")
+                    log.warn(str(e))
             command.run(self)
     return DecoratedCommand