tests: check availability of pyflakes by trying to import pyflakes module

Since e397c6d74652, we use the pyflakes module instead of the pyflakes
executable. As was pointed out during the review, the hghave check can be
rewritten to try to import the pyflakes module instead of spawning a new
subprocess.

tests/hghave.py

@@ -1,1073 +1,1076 b''
 from __future__ import absolute_import, print_function
 
 import distutils.version
 import os
 import re
 import socket
 import stat
 import subprocess
 import sys
 import tempfile
 
 tempprefix = 'hg-hghave-'
 
 checks = {
     "true": (lambda: True, "yak shaving"),
     "false": (lambda: False, "nail clipper"),
 }
 
 try:
     import msvcrt
 
     msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
     msvcrt.setmode(sys.stderr.fileno(), os.O_BINARY)
 except ImportError:
     pass
 
 stdout = getattr(sys.stdout, 'buffer', sys.stdout)
 stderr = getattr(sys.stderr, 'buffer', sys.stderr)
 
 if sys.version_info[0] >= 3:
 
     def _sys2bytes(p):
         if p is None:
             return p
         return p.encode('utf-8')
 
     def _bytes2sys(p):
         if p is None:
             return p
         return p.decode('utf-8')
 
 
 else:
 
     def _sys2bytes(p):
         return p
 
     _bytes2sys = _sys2bytes
 
 
 def check(name, desc):
     """Registers a check function for a feature."""
 
     def decorator(func):
         checks[name] = (func, desc)
         return func
 
     return decorator
 
 
 def checkvers(name, desc, vers):
     """Registers a check function for each of a series of versions.
 
     vers can be a list or an iterator.
 
     Produces a series of feature checks that have the form <name><vers> without
     any punctuation (even if there's punctuation in 'vers'; i.e. this produces
     'py38', not 'py3.8' or 'py-38')."""
 
     def decorator(func):
         def funcv(v):
             def f():
                 return func(v)
 
             return f
 
         for v in vers:
             v = str(v)
             f = funcv(v)
             checks['%s%s' % (name, v.replace('.', ''))] = (f, desc % v)
         return func
 
     return decorator
 
 
 def checkfeatures(features):
     result = {
         'error': [],
         'missing': [],
         'skipped': [],
     }
 
     for feature in features:
         negate = feature.startswith('no-')
         if negate:
             feature = feature[3:]
 
         if feature not in checks:
             result['missing'].append(feature)
             continue
 
         check, desc = checks[feature]
         try:
             available = check()
         except Exception:
             result['error'].append('hghave check failed: %s' % feature)
             continue
 
         if not negate and not available:
             result['skipped'].append('missing feature: %s' % desc)
         elif negate and available:
             result['skipped'].append('system supports %s' % desc)
 
     return result
 
 
 def require(features):
     """Require that features are available, exiting if not."""
     result = checkfeatures(features)
 
     for missing in result['missing']:
         stderr.write(
             ('skipped: unknown feature: %s\n' % missing).encode('utf-8')
         )
     for msg in result['skipped']:
         stderr.write(('skipped: %s\n' % msg).encode('utf-8'))
     for msg in result['error']:
         stderr.write(('%s\n' % msg).encode('utf-8'))
 
     if result['missing']:
         sys.exit(2)
 
     if result['skipped'] or result['error']:
         sys.exit(1)
 
 
 def matchoutput(cmd, regexp, ignorestatus=False):
     """Return the match object if cmd executes successfully and its output
     is matched by the supplied regular expression.
     """
     r = re.compile(regexp)
     p = subprocess.Popen(
         cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT
     )
     s = p.communicate()[0]
     ret = p.returncode
     return (ignorestatus or not ret) and r.search(s)
 
 
 @check("baz", "GNU Arch baz client")
 def has_baz():
     return matchoutput('baz --version 2>&1', br'baz Bazaar version')
 
 
 @check("bzr", "Canonical's Bazaar client")
 def has_bzr():
     try:
         import bzrlib
         import bzrlib.bzrdir
         import bzrlib.errors
         import bzrlib.revision
         import bzrlib.revisionspec
 
         bzrlib.revisionspec.RevisionSpec
         return bzrlib.__doc__ is not None
     except (AttributeError, ImportError):
         return False
 
 
 @checkvers("bzr", "Canonical's Bazaar client >= %s", (1.14,))
 def has_bzr_range(v):
     major, minor = v.split('rc')[0].split('.')[0:2]
     try:
         import bzrlib
 
         return bzrlib.__doc__ is not None and bzrlib.version_info[:2] >= (
             int(major),
             int(minor),
         )
     except ImportError:
         return False
 
 
 @check("chg", "running with chg")
 def has_chg():
     return 'CHGHG' in os.environ
 
 
 @check("cvs", "cvs client/server")
 def has_cvs():
     re = br'Concurrent Versions System.*?server'
     return matchoutput('cvs --version 2>&1', re) and not has_msys()
 
 
 @check("cvs112", "cvs client/server 1.12.* (not cvsnt)")
 def has_cvs112():
     re = br'Concurrent Versions System \(CVS\) 1.12.*?server'
     return matchoutput('cvs --version 2>&1', re) and not has_msys()
 
 
 @check("cvsnt", "cvsnt client/server")
 def has_cvsnt():
     re = br'Concurrent Versions System \(CVSNT\) (\d+).(\d+).*\(client/server\)'
     return matchoutput('cvsnt --version 2>&1', re)
 
 
 @check("darcs", "darcs client")
 def has_darcs():
     return matchoutput('darcs --version', br'\b2\.([2-9]|\d{2})', True)
 
 
 @check("mtn", "monotone client (>= 1.0)")
 def has_mtn():
     return matchoutput('mtn --version', br'monotone', True) and not matchoutput(
         'mtn --version', br'monotone 0\.', True
     )
 
 
 @check("eol-in-paths", "end-of-lines in paths")
 def has_eol_in_paths():
     try:
         fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix, suffix='\n\r')
         os.close(fd)
         os.remove(path)
         return True
     except (IOError, OSError):
         return False
 
 
 @check("execbit", "executable bit")
 def has_executablebit():
     try:
         EXECFLAGS = stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
         fh, fn = tempfile.mkstemp(dir='.', prefix=tempprefix)
         try:
             os.close(fh)
             m = os.stat(fn).st_mode & 0o777
             new_file_has_exec = m & EXECFLAGS
             os.chmod(fn, m ^ EXECFLAGS)
             exec_flags_cannot_flip = (os.stat(fn).st_mode & 0o777) == m
         finally:
             os.unlink(fn)
     except (IOError, OSError):
         # we don't care, the user probably won't be able to commit anyway
         return False
     return not (new_file_has_exec or exec_flags_cannot_flip)
 
 
 @check("icasefs", "case insensitive file system")
 def has_icasefs():
     # Stolen from mercurial.util
     fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix)
     os.close(fd)
     try:
         s1 = os.stat(path)
         d, b = os.path.split(path)
         p2 = os.path.join(d, b.upper())
         if path == p2:
             p2 = os.path.join(d, b.lower())
         try:
             s2 = os.stat(p2)
             return s2 == s1
         except OSError:
             return False
     finally:
         os.remove(path)
 
 
 @check("fifo", "named pipes")
 def has_fifo():
     if getattr(os, "mkfifo", None) is None:
         return False
     name = tempfile.mktemp(dir='.', prefix=tempprefix)
     try:
         os.mkfifo(name)
         os.unlink(name)
         return True
     except OSError:
         return False
 
 
 @check("killdaemons", 'killdaemons.py support')
 def has_killdaemons():
     return True
 
 
 @check("cacheable", "cacheable filesystem")
 def has_cacheable_fs():
     from mercurial import util
 
     fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix)
     os.close(fd)
     try:
         return util.cachestat(path).cacheable()
     finally:
         os.remove(path)
 
 
 @check("lsprof", "python lsprof module")
 def has_lsprof():
     try:
         import _lsprof
 
         _lsprof.Profiler  # silence unused import warning
         return True
     except ImportError:
         return False
 
 
 def _gethgversion():
     m = matchoutput('hg --version --quiet 2>&1', br'(\d+)\.(\d+)')
     if not m:
         return (0, 0)
     return (int(m.group(1)), int(m.group(2)))
 
 
 _hgversion = None
 
 
 def gethgversion():
     global _hgversion
     if _hgversion is None:
         _hgversion = _gethgversion()
     return _hgversion
 
 
 @checkvers(
     "hg", "Mercurial >= %s", list([(1.0 * x) / 10 for x in range(9, 99)])
 )
 def has_hg_range(v):
     major, minor = v.split('.')[0:2]
     return gethgversion() >= (int(major), int(minor))
 
 
 @check("rust", "Using the Rust extensions")
 def has_rust():
     """Check is the mercurial currently running is using some rust code"""
     cmd = b'hg debuginstall --quiet 2>&1'
     match = br'checking module policy \(([^)]+)\)'
     policy = matchoutput(cmd, match)
     if not policy:
         return False
     return b'rust' in policy.group(1)
 
 
 @check("hg08", "Mercurial >= 0.8")
 def has_hg08():
     if checks["hg09"][0]():
         return True
     return matchoutput('hg help annotate 2>&1', '--date')
 
 
 @check("hg07", "Mercurial >= 0.7")
 def has_hg07():
     if checks["hg08"][0]():
         return True
     return matchoutput('hg --version --quiet 2>&1', 'Mercurial Distributed SCM')
 
 
 @check("hg06", "Mercurial >= 0.6")
 def has_hg06():
     if checks["hg07"][0]():
         return True
     return matchoutput('hg --version --quiet 2>&1', 'Mercurial version')
 
 
 @check("gettext", "GNU Gettext (msgfmt)")
 def has_gettext():
     return matchoutput('msgfmt --version', br'GNU gettext-tools')
 
 
 @check("git", "git command line client")
 def has_git():
     return matchoutput('git --version 2>&1', br'^git version')
 
 
 def getgitversion():
     m = matchoutput('git --version 2>&1', br'git version (\d+)\.(\d+)')
     if not m:
         return (0, 0)
     return (int(m.group(1)), int(m.group(2)))
 
 
 @check("pygit2", "pygit2 Python library")
 def has_git():
     try:
         import pygit2
 
         pygit2.Oid  # silence unused import
         return True
     except ImportError:
         return False
 
 
 # https://github.com/git-lfs/lfs-test-server
 @check("lfs-test-server", "git-lfs test server")
 def has_lfsserver():
     exe = 'lfs-test-server'
     if has_windows():
         exe = 'lfs-test-server.exe'
     return any(
         os.access(os.path.join(path, exe), os.X_OK)
         for path in os.environ["PATH"].split(os.pathsep)
     )
 
 
 @checkvers("git", "git client (with ext::sh support) version >= %s", (1.9,))
 def has_git_range(v):
     major, minor = v.split('.')[0:2]
     return getgitversion() >= (int(major), int(minor))
 
 
 @check("docutils", "Docutils text processing library")
 def has_docutils():
     try:
         import docutils.core
 
         docutils.core.publish_cmdline  # silence unused import
         return True
     except ImportError:
         return False
 
 
 def getsvnversion():
     m = matchoutput('svn --version --quiet 2>&1', br'^(\d+)\.(\d+)')
     if not m:
         return (0, 0)
     return (int(m.group(1)), int(m.group(2)))
 
 
 @checkvers("svn", "subversion client and admin tools >= %s", (1.3, 1.5))
 def has_svn_range(v):
     major, minor = v.split('.')[0:2]
     return getsvnversion() >= (int(major), int(minor))
 
 
 @check("svn", "subversion client and admin tools")
 def has_svn():
     return matchoutput('svn --version 2>&1', br'^svn, version') and matchoutput(
         'svnadmin --version 2>&1', br'^svnadmin, version'
     )
 
 
 @check("svn-bindings", "subversion python bindings")
 def has_svn_bindings():
     try:
         import svn.core
 
         version = svn.core.SVN_VER_MAJOR, svn.core.SVN_VER_MINOR
         if version < (1, 4):
             return False
         return True
     except ImportError:
         return False
 
 
 @check("p4", "Perforce server and client")
 def has_p4():
     return matchoutput('p4 -V', br'Rev\. P4/') and matchoutput(
         'p4d -V', br'Rev\. P4D/'
     )
 
 
 @check("symlink", "symbolic links")
 def has_symlink():
     # mercurial.windows.checklink() is a hard 'no' at the moment
     if os.name == 'nt' or getattr(os, "symlink", None) is None:
         return False
     name = tempfile.mktemp(dir='.', prefix=tempprefix)
     try:
         os.symlink(".", name)
         os.unlink(name)
         return True
     except (OSError, AttributeError):
         return False
 
 
 @check("hardlink", "hardlinks")
 def has_hardlink():
     from mercurial import util
 
     fh, fn = tempfile.mkstemp(dir='.', prefix=tempprefix)
     os.close(fh)
     name = tempfile.mktemp(dir='.', prefix=tempprefix)
     try:
         util.oslink(_sys2bytes(fn), _sys2bytes(name))
         os.unlink(name)
         return True
     except OSError:
         return False
     finally:
         os.unlink(fn)
 
 
 @check("hardlink-whitelisted", "hardlinks on whitelisted filesystems")
 def has_hardlink_whitelisted():
     from mercurial import util
 
     try:
         fstype = util.getfstype(b'.')
     except OSError:
         return False
     return fstype in util._hardlinkfswhitelist
 
 
 @check("rmcwd", "can remove current working directory")
 def has_rmcwd():
     ocwd = os.getcwd()
     temp = tempfile.mkdtemp(dir='.', prefix=tempprefix)
     try:
         os.chdir(temp)
         # On Linux, 'rmdir .' isn't allowed, but the other names are okay.
         # On Solaris and Windows, the cwd can't be removed by any names.
         os.rmdir(os.getcwd())
         return True
     except OSError:
         return False
     finally:
         os.chdir(ocwd)
         # clean up temp dir on platforms where cwd can't be removed
         try:
             os.rmdir(temp)
         except OSError:
             pass
 
 
 @check("tla", "GNU Arch tla client")
 def has_tla():
     return matchoutput('tla --version 2>&1', br'The GNU Arch Revision')
 
 
 @check("gpg", "gpg client")
 def has_gpg():
     return matchoutput('gpg --version 2>&1', br'GnuPG')
 
 
 @check("gpg2", "gpg client v2")
 def has_gpg2():
     return matchoutput('gpg --version 2>&1', br'GnuPG[^0-9]+2\.')
 
 
 @check("gpg21", "gpg client v2.1+")
 def has_gpg21():
     return matchoutput('gpg --version 2>&1', br'GnuPG[^0-9]+2\.(?!0)')
 
 
 @check("unix-permissions", "unix-style permissions")
 def has_unix_permissions():
     d = tempfile.mkdtemp(dir='.', prefix=tempprefix)
     try:
         fname = os.path.join(d, 'foo')
         for umask in (0o77, 0o07, 0o22):
             os.umask(umask)
             f = open(fname, 'w')
             f.close()
             mode = os.stat(fname).st_mode
             os.unlink(fname)
             if mode & 0o777 != ~umask & 0o666:
                 return False
         return True
     finally:
         os.rmdir(d)
 
 
 @check("unix-socket", "AF_UNIX socket family")
 def has_unix_socket():
     return getattr(socket, 'AF_UNIX', None) is not None
 
 
 @check("root", "root permissions")
 def has_root():
     return getattr(os, 'geteuid', None) and os.geteuid() == 0
 
 
 @check("pyflakes", "Pyflakes python linter")
 def has_pyflakes():
-    return matchoutput(
-        "sh -c \"echo 'import re' 2>&1 | $PYTHON -m pyflakes\"",
-        br"<stdin>:1: 're' imported but unused",
-        True,
-    )
+    try:
+        import pyflakes
+
+        pyflakes.__version__
+    except ImportError:
+        return False
+    else:
+        return True
 
 
 @check("pylint", "Pylint python linter")
 def has_pylint():
     return matchoutput("pylint --help", br"Usage:  pylint", True)
 
 
 @check("clang-format", "clang-format C code formatter")
 def has_clang_format():
     m = matchoutput('clang-format --version', br'clang-format version (\d)')
     # style changed somewhere between 4.x and 6.x
     return m and int(m.group(1)) >= 6
 
 
 @check("jshint", "JSHint static code analysis tool")
 def has_jshint():
     return matchoutput("jshint --version 2>&1", br"jshint v")
 
 
 @check("pygments", "Pygments source highlighting library")
 def has_pygments():
     try:
         import pygments
 
         pygments.highlight  # silence unused import warning
         return True
     except ImportError:
         return False
 
 
 @check("pygments25", "Pygments version >= 2.5")
 def pygments25():
     try:
         import pygments
 
         v = pygments.__version__
     except ImportError:
         return False
 
     parts = v.split(".")
     major = int(parts[0])
     minor = int(parts[1])
 
     return (major, minor) >= (2, 5)
 
 
 @check("outer-repo", "outer repo")
 def has_outer_repo():
     # failing for other reasons than 'no repo' imply that there is a repo
     return not matchoutput('hg root 2>&1', br'abort: no repository found', True)
 
 
 @check("ssl", "ssl module available")
 def has_ssl():
     try:
         import ssl
 
         ssl.CERT_NONE
         return True
     except ImportError:
         return False
 
 
 @check("sslcontext", "python >= 2.7.9 ssl")
 def has_sslcontext():
     try:
         import ssl
 
         ssl.SSLContext
         return True
     except (ImportError, AttributeError):
         return False
 
 
 @check("defaultcacerts", "can verify SSL certs by system's CA certs store")
 def has_defaultcacerts():
     from mercurial import sslutil, ui as uimod
 
     ui = uimod.ui.load()
     return sslutil._defaultcacerts(ui) or sslutil._canloaddefaultcerts
 
 
 @check("defaultcacertsloaded", "detected presence of loaded system CA certs")
 def has_defaultcacertsloaded():
     import ssl
     from mercurial import sslutil, ui as uimod
 
     if not has_defaultcacerts():
         return False
     if not has_sslcontext():
         return False
 
     ui = uimod.ui.load()
     cafile = sslutil._defaultcacerts(ui)
     ctx = ssl.create_default_context()
     if cafile:
         ctx.load_verify_locations(cafile=cafile)
     else:
         ctx.load_default_certs()
 
     return len(ctx.get_ca_certs()) > 0
 
 
 @check("tls1.2", "TLS 1.2 protocol support")
 def has_tls1_2():
     from mercurial import sslutil
 
     return b'tls1.2' in sslutil.supportedprotocols
 
 
 @check("windows", "Windows")
 def has_windows():
     return os.name == 'nt'
 
 
 @check("system-sh", "system() uses sh")
 def has_system_sh():
     return os.name != 'nt'
 
 
 @check("serve", "platform and python can manage 'hg serve -d'")
 def has_serve():
     return True
 
 
 @check("test-repo", "running tests from repository")
 def has_test_repo():
     t = os.environ["TESTDIR"]
     return os.path.isdir(os.path.join(t, "..", ".hg"))
 
 
 @check("tic", "terminfo compiler and curses module")
 def has_tic():
     try:
         import curses
 
         curses.COLOR_BLUE
         return matchoutput('test -x "`which tic`"', br'')
     except (ImportError, AttributeError):
         return False
 
 
 @check("xz", "xz compression utility")
 def has_xz():
     # When Windows invokes a subprocess in shell mode, it uses `cmd.exe`, which
     # only knows `where`, not `which`.  So invoke MSYS shell explicitly.
     return matchoutput("sh -c 'test -x \"`which xz`\"'", b'')
 
 
 @check("msys", "Windows with MSYS")
 def has_msys():
     return os.getenv('MSYSTEM')
 
 
 @check("aix", "AIX")
 def has_aix():
     return sys.platform.startswith("aix")
 
 
 @check("osx", "OS X")
 def has_osx():
     return sys.platform == 'darwin'
 
 
 @check("osxpackaging", "OS X packaging tools")
 def has_osxpackaging():
     try:
         return (
             matchoutput('pkgbuild', br'Usage: pkgbuild ', ignorestatus=1)
             and matchoutput(
                 'productbuild', br'Usage: productbuild ', ignorestatus=1
             )
             and matchoutput('lsbom', br'Usage: lsbom', ignorestatus=1)
             and matchoutput('xar --help', br'Usage: xar', ignorestatus=1)
         )
     except ImportError:
         return False
 
 
 @check('linuxormacos', 'Linux or MacOS')
 def has_linuxormacos():
     # This isn't a perfect test for MacOS. But it is sufficient for our needs.
     return sys.platform.startswith(('linux', 'darwin'))
 
 
 @check("docker", "docker support")
 def has_docker():
     pat = br'A self-sufficient runtime for'
     if matchoutput('docker --help', pat):
         if 'linux' not in sys.platform:
             # TODO: in theory we should be able to test docker-based
             # package creation on non-linux using boot2docker, but in
             # practice that requires extra coordination to make sure
             # $TESTTEMP is going to be visible at the same path to the
             # boot2docker VM. If we figure out how to verify that, we
             # can use the following instead of just saying False:
             # return 'DOCKER_HOST' in os.environ
             return False
 
         return True
     return False
 
 
 @check("debhelper", "debian packaging tools")
 def has_debhelper():
     # Some versions of dpkg say `dpkg', some say 'dpkg' (` vs ' on the first
     # quote), so just accept anything in that spot.
     dpkg = matchoutput(
         'dpkg --version', br"Debian .dpkg' package management program"
     )
     dh = matchoutput(
         'dh --help', br'dh is a part of debhelper.', ignorestatus=True
     )
     dh_py2 = matchoutput(
         'dh_python2 --help', br'other supported Python versions'
     )
     # debuild comes from the 'devscripts' package, though you might want
     # the 'build-debs' package instead, which has a dependency on devscripts.
     debuild = matchoutput(
         'debuild --help', br'to run debian/rules with given parameter'
     )
     return dpkg and dh and dh_py2 and debuild
 
 
 @check(
     "debdeps", "debian build dependencies (run dpkg-checkbuilddeps in contrib/)"
 )
 def has_debdeps():
     # just check exit status (ignoring output)
     path = '%s/../contrib/packaging/debian/control' % os.environ['TESTDIR']
     return matchoutput('dpkg-checkbuilddeps %s' % path, br'')
 
 
 @check("demandimport", "demandimport enabled")
 def has_demandimport():
     # chg disables demandimport intentionally for performance wins.
     return (not has_chg()) and os.environ.get('HGDEMANDIMPORT') != 'disable'
 
 
 # Add "py27", "py35", ... as possible feature checks. Note that there's no
 # punctuation here.
 @checkvers("py", "Python >= %s", (2.7, 3.5, 3.6, 3.7, 3.8, 3.9))
 def has_python_range(v):
     major, minor = v.split('.')[0:2]
     py_major, py_minor = sys.version_info.major, sys.version_info.minor
 
     return (py_major, py_minor) >= (int(major), int(minor))
 
 
 @check("py3", "running with Python 3.x")
 def has_py3():
     return 3 == sys.version_info[0]
 
 
 @check("py3exe", "a Python 3.x interpreter is available")
 def has_python3exe():
     return matchoutput('python3 -V', br'^Python 3.(5|6|7|8|9)')
 
 
 @check("pure", "running with pure Python code")
 def has_pure():
     return any(
         [
             os.environ.get("HGMODULEPOLICY") == "py",
             os.environ.get("HGTEST_RUN_TESTS_PURE") == "--pure",
         ]
     )
 
 
 @check("slow", "allow slow tests (use --allow-slow-tests)")
 def has_slow():
     return os.environ.get('HGTEST_SLOW') == 'slow'
 
 
 @check("hypothesis", "Hypothesis automated test generation")
 def has_hypothesis():
     try:
         import hypothesis
 
         hypothesis.given
         return True
     except ImportError:
         return False
 
 
 @check("unziplinks", "unzip(1) understands and extracts symlinks")
 def unzip_understands_symlinks():
     return matchoutput('unzip --help', br'Info-ZIP')
 
 
 @check("zstd", "zstd Python module available")
 def has_zstd():
     try:
         import mercurial.zstd
 
         mercurial.zstd.__version__
         return True
     except ImportError:
         return False
 
 
 @check("devfull", "/dev/full special file")
 def has_dev_full():
     return os.path.exists('/dev/full')
 
 
 @check("ensurepip", "ensurepip module")
 def has_ensurepip():
     try:
         import ensurepip
 
         ensurepip.bootstrap
         return True
     except ImportError:
         return False
 
 
 @check("virtualenv", "Python virtualenv support")
 def has_virtualenv():
     try:
         import virtualenv
 
         virtualenv.ACTIVATE_SH
         return True
     except ImportError:
         return False
 
 
 @check("fsmonitor", "running tests with fsmonitor")
 def has_fsmonitor():
     return 'HGFSMONITOR_TESTS' in os.environ
 
 
 @check("fuzzywuzzy", "Fuzzy string matching library")
 def has_fuzzywuzzy():
     try:
         import fuzzywuzzy
 
         fuzzywuzzy.__version__
         return True
     except ImportError:
         return False
 
 
 @check("clang-libfuzzer", "clang new enough to include libfuzzer")
 def has_clang_libfuzzer():
     mat = matchoutput('clang --version', br'clang version (\d)')
     if mat:
         # libfuzzer is new in clang 6
         return int(mat.group(1)) > 5
     return False
 
 
 @check("clang-6.0", "clang 6.0 with version suffix (libfuzzer included)")
 def has_clang60():
     return matchoutput('clang-6.0 --version', br'clang version 6\.')
 
 
 @check("xdiff", "xdiff algorithm")
 def has_xdiff():
     try:
         from mercurial import policy
 
         bdiff = policy.importmod('bdiff')
         return bdiff.xdiffblocks(b'', b'') == [(0, 0, 0, 0)]
     except (ImportError, AttributeError):
         return False
 
 
 @check('extraextensions', 'whether tests are running with extra extensions')
 def has_extraextensions():
     return 'HGTESTEXTRAEXTENSIONS' in os.environ
 
 
 def getrepofeatures():
     """Obtain set of repository features in use.
 
     HGREPOFEATURES can be used to define or remove features. It contains
     a space-delimited list of feature strings. Strings beginning with ``-``
     mean to remove.
     """
     # Default list provided by core.
     features = {
         'bundlerepo',
         'revlogstore',
         'fncache',
     }
 
     # Features that imply other features.
     implies = {
         'simplestore': ['-revlogstore', '-bundlerepo', '-fncache'],
     }
 
     for override in os.environ.get('HGREPOFEATURES', '').split(' '):
         if not override:
             continue
 
         if override.startswith('-'):
             if override[1:] in features:
                 features.remove(override[1:])
         else:
             features.add(override)
 
             for imply in implies.get(override, []):
                 if imply.startswith('-'):
                     if imply[1:] in features:
                         features.remove(imply[1:])
                 else:
                     features.add(imply)
 
     return features
 
 
 @check('reporevlogstore', 'repository using the default revlog store')
 def has_reporevlogstore():
     return 'revlogstore' in getrepofeatures()
 
 
 @check('reposimplestore', 'repository using simple storage extension')
 def has_reposimplestore():
     return 'simplestore' in getrepofeatures()
 
 
 @check('repobundlerepo', 'whether we can open bundle files as repos')
 def has_repobundlerepo():
     return 'bundlerepo' in getrepofeatures()
 
 
 @check('repofncache', 'repository has an fncache')
 def has_repofncache():
     return 'fncache' in getrepofeatures()
 
 
 @check('sqlite', 'sqlite3 module is available')
 def has_sqlite():
     try:
         import sqlite3
 
         version = sqlite3.sqlite_version_info
     except ImportError:
         return False
 
     if version < (3, 8, 3):
         # WITH clause not supported
         return False
 
     return matchoutput('sqlite3 -version', br'^3\.\d+')
 
 
 @check('vcr', 'vcr http mocking library')
 def has_vcr():
     try:
         import vcr
 
         vcr.VCR
         return True
     except (ImportError, AttributeError):
         pass
     return False
 
 
 @check('emacs', 'GNU Emacs')
 def has_emacs():
     # Our emacs lisp uses `with-eval-after-load` which is new in emacs
     # 24.4, so we allow emacs 24.4, 24.5, and 25+ (24.5 was the last
     # 24 release)
     return matchoutput('emacs --version', b'GNU Emacs 2(4.4|4.5|5|6|7|8|9)')
 
 
 @check('black', 'the black formatter for python')
 def has_black():
     blackcmd = 'black --version'
     version_regex = b'black, version ([0-9a-b.]+)'
     version = matchoutput(blackcmd, version_regex)
     sv = distutils.version.StrictVersion
     return version and sv(_bytes2sys(version.group(1))) >= sv('19.10b0')
 
 
 @check('pytype', 'the pytype type checker')
 def has_pytype():
     pytypecmd = 'pytype --version'
     version = matchoutput(pytypecmd, b'[0-9a-b.]+')
     sv = distutils.version.StrictVersion
     return version and sv(_bytes2sys(version.group(0))) >= sv('2019.10.17')
 
 
 @check("rustfmt", "rustfmt tool")
 def has_rustfmt():
     # We use Nightly's rustfmt due to current unstable config options.
     return matchoutput(
         '`rustup which --toolchain nightly rustfmt` --version', b'rustfmt'
     )