Entry points with extra requirements doesn't work if `.dist-info` is used since setuptools 20.8.1

[jun66j5]

With setuptools 20.8.1: trac.mimeview.pygments would be imported even though pygments package is not resolved. Then, an ImportError would be raised. Latest of setuptools 26.0.0 has the same behavior.

$ /dev/shm/setuptools-20.8.1/bin/pip freeze
Genshi==0.6
Trac==1.0.12
argparse==1.2.1
wsgiref==0.1.2
$ /dev/shm/setuptools-20.8.1/bin/python
Python 2.7.6 (default, Jun 22 2015, 17:58:13)
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from pkg_resources import working_set
>>> for ep in working_set.iter_entry_points('trac.plugins'):
...   if 'pygments' in ep.extras:
...     break
...
>>> ep
EntryPoint.parse('trac.mimeview.pygments = trac.mimeview.pygments [pygments]')
>>> ep.load(require=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/dev/shm/setuptools-20.8.1/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2229, in load
    return self.resolve()
  File "/dev/shm/setuptools-20.8.1/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2235, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/dev/shm/setuptools-20.8.1/local/lib/python2.7/site-packages/trac/mimeview/pygments.py", line 16, in <module>
    import pygments
ImportError: No module named pygments
>>>

With setuptools 20.4.0: trac.mimeview.pygments wouldn't be imported and DistributionNotFound would be raised because pygments package is not resolved.

$ /dev/shm/setuptools-20.4.0/bin/pip freeze
Genshi==0.6
Trac==1.0.12
argparse==1.2.1
wsgiref==0.1.2
$ /dev/shm/setuptools-20.4.0/bin/python
Python 2.7.6 (default, Jun 22 2015, 17:58:13)
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from pkg_resources import working_set
>>> for ep in working_set.iter_entry_points('trac.plugins'):
...   if 'pygments' in ep.extras:
...     break
...
>>> ep
EntryPoint.parse('trac.mimeview.pygments = trac.mimeview.pygments [pygments]')
>>> from pkg_resources import get_distribution
>>> ep.load(require=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/dev/shm/setuptools-20.4.0/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2202, in load
    self.require(*args, **kwargs)
  File "/dev/shm/setuptools-20.4.0/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2219, in require
    items = working_set.resolve(reqs, env, installer)
  File "/dev/shm/setuptools-20.4.0/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 830, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'Pygments>=0.6; extra == "pygments"' distribution was not found and is required by the application

We expect DistributionNotFound (or UnknownExtra?) is raised in this case. See also https://trac.edgewall.org/ticket/12282#comment:7.

[jun66j5]

DistributionNotFound is raised as expected if the modules is installed with .egg-info. The extra requirements works fine with .egg-info.

$ /dev/shm/setuptools/bin/pip list --local
Genshi (0.7)
pip (1.5.4)
setuptools (27.2.0)
Trac (1.0.13)
$ ls /dev/shm/setuptools/lib/python2.7/site-packages/ | grep Trac
Trac-1.0.13-py2.7.egg-info
$ /dev/shm/setuptools/bin/python
...
>>> ep
EntryPoint.parse('trac.mimeview.pygments = trac.mimeview.pygments [pygments]')
>>> ep.dist
Trac 1.0.13 (/run/shm/setuptools/lib/python2.7/site-packages)
>>> ep.load(require=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/dev/shm/setuptools/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2257, in load
    self.require(*args, **kwargs)
  File "/dev/shm/setuptools/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2274, in require
    items = working_set.resolve(reqs, env, installer)
  File "/dev/shm/setuptools/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 854, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'Pygments>=0.6' distribution was not found and is required by the application

DistributionNotFound is not raised if the package is installed with .dist-info. The extra requirements doesn't work with .dist-info.

$ ls /dev/shm/setuptools/lib/python2.7/site-packages/ | grep Trac
Trac-1.0.13.dist-info
$ /dev/shm/setuptools/bin/python
>>> ep.load(require=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/dev/shm/setuptools/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2258, in load
    return self.resolve()
  File "/dev/shm/setuptools/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2264, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/dev/shm/setuptools/local/lib/python2.7/site-packages/trac/mimeview/pygments.py", line 16, in <module>
    import pygments
ImportError: No module named pygments