Code review comment for ~kissiel/checkbox-support:fix-missing-reqs

Random thought, not sure if you care, but this should work in recent pythons at least:
     install_requires=[
          'lxml >= 2.3',
          'pyparsing >= 2.0.0',
                 'requests >= 1.0',
                 'requests_unixsocket >= 0.1.2',
                 *(['configparser'] if sys.version_info.major == 2 else []),
     ]
just depends whether you prefer appending it with + or keeping it inline