Update to 3.4.2
    
    $ pytest-2.7
    Traceback (most recent call last):
      File "/usr/bin/pytest-2.7", line 6, in <module>
        from pkg_resources import load_entry_point
      File "/usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3147, in <module>
        @_call_aside
      File "/usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3131, in _call_aside
        f(*args, **kwargs)
      File "/usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3160, in _initialize_master_working_set
        working_set = WorkingSet._build_master()
      File "/usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 666, in _build_master
        ws.require(__requires__)
      File "/usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 984, in require
        needed = self.resolve(parse_requirements(requirements))
      File "/usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 870, in resolve
        raise DistributionNotFound(req, requirers)
    pkg_resources.DistributionNotFound: The 'pluggy<0.7,>=0.5' distribution was not found and is required by pytest
    
    etc.