There is a version conflict between multiple gunicorn installed on ubuntu. I don't know how to resolve it.

problem description

multiple gunicorn are installed on ubuntu. There is a version conflict. I have pip3 install gunicorn and easy install before. Is random play, now the emergence of VersionConflict do not know how to deal with.

the platform version of the problem and what methods you have tried

remove and easy install-m pass

what result do you expect? What is the error message actually seen?

enter gonicorn on the terminal and report an error as follows:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 635, in _build_master
    ws.require(__requires__)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 943, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 834, in resolve
    raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.VersionConflict: (gunicorn 19.9.0 (/home/rex//gunicorn), Requirement.parse("gunicorn==19.4.5"))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/gunicorn", line 5, in <module>
    from pkg_resources import load_entry_point
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2927, in <module>
    @_call_aside
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2913, in _call_aside
    f(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2940, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 637, in _build_master
    return cls._build_from_requirements(__requires__)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 650, in _build_from_requirements
    dists = ws.resolve(reqs, Environment())
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 829, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The "gunicorn==19.4.5" distribution was not found and is required by the application