setup.py: support Paste 3.0.x

In a fresh virtualenv on the stable branch, pastescript 3.0.0 is installed
which depends on paste 3.0.x. Using this virtualenv to upgrade to the
default branch, using 'pip install --upgrade -e .' fails because on the
default branch, the paste version is restricted with '>= 2.0.3, < 3'.
Following error occurs:

pastescript 3.0.0 has requirement Paste>=3.0, but you'll have paste 2.0.3 which is incompatible.
...
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File ".../kallithea/kallithea-release/setup.py", line 160, in <module>
        """,
      File "/usr/lib64/python2.7/distutils/core.py", line 151, in setup
        dist.run_commands()
      File "/usr/lib64/python2.7/distutils/dist.py", line 953, in run_commands
        self.run_command(cmd)
      File "/usr/lib64/python2.7/distutils/dist.py", line 972, in run_command
        cmd_obj.run()
      File ".../kallithea/venv/kallithea-release/lib/python2.7/site-packages/setuptools/command/develop.py", line 36, in run
        self.install_for_development()
      File ".../kallithea/venv/kallithea-release/lib/python2.7/site-packages/setuptools/command/develop.py", line 117, in install_for_development
        self.run_command('egg_info')
      File "/usr/lib64/python2.7/distutils/cmd.py", line 326, in run_command
        self.distribution.run_command(command)
      File "/usr/lib64/python2.7/distutils/dist.py", line 972, in run_command
        cmd_obj.run()
      File ".../kallithea/venv/kallithea-release/lib/python2.7/site-packages/setuptools/command/egg_info.py", line 270, in run
        ep.require(installer=installer)
      File ".../kallithea/venv/kallithea-release/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2307, in require
        items = working_set.resolve(reqs, env, installer)
      File ".../kallithea/venv/kallithea-release/lib/python2.7/site-packages/pkg_resources/__init__.py", line 854, in resolve
        raise VersionConflict(dist, req).with_context(dependent_req)
    pkg_resources.VersionConflict: (Paste 2.0.3 (.../kallithea/venv/kallithea-release/lib/python2.7/site-packages), Requirement.parse('Paste>=3.0'))


The '< 3' restriction is introduced with commit
e1ab826131334150b1f003e26de3207c34fc6e67 in January 2017, at which point
2.0.3 was the latest version. Version 3.0.0 was introduced in October 2018.

Paste has a new maintainer and moved to github, after years of
inactivity (March 2016 -> Oct 2018). There have AFAICS not been
incompatible changes. This analysis is based on:
- the news file: https://pythonpaste.readthedocs.io/en/latest/news.html
- the commit message of the 3.0.0 release:
(https://github.com/cdent/paste/commit/9ceef07267ba83ea5c00533f85f9edf9ba38cd71)

"This is for the sake of getting something out there, including
fixes to get stuff working with Python 3.7."

- and a walk through the commits since 2.0.3 on github
(https://github.com/cdent/paste/commits/master).

setup.py

@@ -1,161 +1,161 b''
 #!/usr/bin/env python2
 # -*- coding: utf-8 -*-
 import os
 import sys
 import platform
 
 if sys.version_info < (2, 6) or sys.version_info >= (3,):
     raise Exception('Kallithea requires python 2.6 or 2.7')
 
 
 here = os.path.abspath(os.path.dirname(__file__))
 
 
 def _get_meta_var(name, data, callback_handler=None):
     import re
     matches = re.compile(r'(?:%s)\s*=\s*(.*)' % name).search(data)
     if matches:
         if not callable(callback_handler):
             callback_handler = lambda v: v
 
         return callback_handler(eval(matches.groups()[0]))
 
 _meta = open(os.path.join(here, 'kallithea', '__init__.py'), 'rb')
 _metadata = _meta.read()
 _meta.close()
 
 callback = lambda V: ('.'.join(map(str, V[:3])) + '.'.join(V[3:]))
 __version__ = _get_meta_var('VERSION', _metadata, callback)
 __license__ = _get_meta_var('__license__', _metadata)
 __author__ = _get_meta_var('__author__', _metadata)
 __url__ = _get_meta_var('__url__', _metadata)
 # defines current platform
 __platform__ = platform.system()
 
 is_windows = __platform__ in ['Windows']
 
 requirements = [
     "alembic >= 0.8.0, < 1.1",
     "gearbox < 1",
     "waitress >= 0.8.8, < 1.2",
     "WebOb >= 1.7, < 1.8", # turbogears2 2.3.12 requires WebOb<1.8.0
     "backlash >= 0.1.2, < 1",
     "TurboGears2 >= 2.3.10, < 3",
     "tgext.routes >= 0.2.0, < 1",
     "Beaker >= 1.7.0, < 2",
     "WebHelpers >= 1.3, < 1.4",
     "FormEncode >= 1.2.4, < 1.4",
     "SQLAlchemy >= 1.1, < 1.3",
     "Mako >= 0.9.0, < 1.1",
     "Pygments >= 1.5, < 2.3",
     "Whoosh >= 2.5.0, < 2.8",
     "celery >= 3.1, < 4.0", # celery 4 doesn't work
     "Babel >= 0.9.6, < 2.7",
     "python-dateutil >= 1.5.0, < 2.8",
     "Markdown >= 2.2.1, < 2.7",
     "docutils >= 0.8.1, < 0.15",
     "URLObject >= 2.3.4, < 2.5",
     "Routes >= 1.13, < 2",
     "dulwich >= 0.14.1, < 0.20",
     "mercurial >= 4.1.1, < 4.9",
     "decorator >= 3.3.2, < 4.4",
-    "Paste >= 2.0.3, < 3",
+    "Paste >= 2.0.3, < 3.1",
     "bleach >= 3.0, < 3.1",
     "Click >= 7.0, < 8",
 ]
 
 if sys.version_info < (2, 7):
     requirements.append("importlib == 1.0.1")
     requirements.append("argparse")
 
 if not is_windows:
     requirements.append("bcrypt >= 3.1.0, < 3.2")
 
 dependency_links = [
 ]
 
 classifiers = [
     'Development Status :: 4 - Beta',
     'Environment :: Web Environment',
     'Framework :: Pylons',
     'Intended Audience :: Developers',
     'License :: OSI Approved :: GNU General Public License (GPL)',
     'Operating System :: OS Independent',
     'Programming Language :: Python',
     'Programming Language :: Python :: 2.6',
     'Programming Language :: Python :: 2.7',
     'Topic :: Software Development :: Version Control',
 ]
 
 
 # additional files from project that goes somewhere in the filesystem
 # relative to sys.prefix
 data_files = []
 
 description = ('Kallithea is a fast and powerful management tool '
                'for Mercurial and Git with a built in push/pull server, '
                'full text search and code-review.')
 
 keywords = ' '.join([
     'kallithea', 'mercurial', 'git', 'code review',
     'repo groups', 'ldap', 'repository management', 'hgweb replacement',
     'hgwebdir', 'gitweb replacement', 'serving hgweb',
 ])
 
 # long description
 README_FILE = 'README.rst'
 try:
     long_description = open(README_FILE).read()
 except IOError as err:
     sys.stderr.write(
         "[WARNING] Cannot find file specified as long_description (%s)\n"
         % README_FILE
     )
     long_description = description
 
 import setuptools
 
 # monkey patch setuptools to use distutils owner/group functionality
 from setuptools.command import sdist
 sdist_org = sdist.sdist
 class sdist_new(sdist_org):
     def initialize_options(self):
         sdist_org.initialize_options(self)
         self.owner = self.group = 'root'
 sdist.sdist = sdist_new
 
 packages = setuptools.find_packages(exclude=['ez_setup'])
 
 setuptools.setup(
     name='Kallithea',
     version=__version__,
     description=description,
     long_description=long_description,
     keywords=keywords,
     license=__license__,
     author=__author__,
     author_email='[e-mail]',
     dependency_links=dependency_links,
     url=__url__,
     install_requires=requirements,
     classifiers=classifiers,
     data_files=data_files,
     packages=packages,
     include_package_data=True,
     message_extractors={'kallithea': [
             ('**.py', 'python', None),
             ('templates/**.mako', 'mako', {'input_encoding': 'utf-8'}),
             ('templates/**.html', 'mako', {'input_encoding': 'utf-8'}),
             ('public/**', 'ignore', None)]},
     zip_safe=False,
     entry_points="""
     [console_scripts]
     kallithea-api =    kallithea.bin.kallithea_api:main
     kallithea-gist =   kallithea.bin.kallithea_gist:main
     kallithea-config = kallithea.bin.kallithea_config:main
     kallithea-cli =    kallithea.bin.kallithea_cli:cli
 
     [paste.app_factory]
     main = kallithea.config.middleware:make_app
     """,
 )