title: pip --version command show error, how to fix it?
body: <p>I am using MacOS Mojave.</p>
  
  <p>I installed <code>python</code> using brew command. And before i could use both <code>pip --version</code>, and <code>pip3 --version</code>. I saw that i had previous version of <code>pip</code>. I ran the command <code>pip install --upgrade pip</code>.  When i run <code>python --version</code> its how me the version. When i run <code>pip3 --version</code> i get this: </p>
  
  <pre><code>pip 19.2.3 from /usr/local/lib/python3.7/site-packages/pip (python 3.7)
  </code></pre>
  
  <p>But when i run <code>pip --version</code> , its gives me error:</p>
  
  <pre><code>pip --version
  Traceback (most recent call last):
    File "/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py", line 583, in _build_master
      ws.require(__requires__)
    File "/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py", line 900, in require
      needed = self.resolve(parse_requirements(requirements))
    File "/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py", line 791, in resolve
      raise VersionConflict(dist, req).with_context(dependent_req)
  pkg_resources.VersionConflict: (pip 19.2.3 (/usr/local/lib/python3.7/site-packages), Requirement.parse('pip==19.1.1'))
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File "/usr/local/opt/python/libexec/bin/pip", line 6, in &lt;module&gt;
      from pkg_resources import load_entry_point
    File "/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py", line 3241, in &lt;module&gt;
      @_call_aside
    File "/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py", line 3225, in _call_aside
      f(*args, **kwargs)
    File "/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py", line 3254, in _initialize_master_working_set
      working_set = WorkingSet._build_master()
    File "/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py", line 585, in _build_master
      return cls._build_from_requirements(__requires__)
    File "/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py", line 598, in _build_from_requirements
      dists = ws.resolve(reqs, Environment())
    File "/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py", line 786, in resolve
      raise DistributionNotFound(req, requirers)
  pkg_resources.DistributionNotFound: The 'pip==19.1.1' distribution was not found and is required by the application
  </code></pre>
  
  <p>How can i fix this? I tried to run <code>brew doctor</code> and tried to find any solution with no luck. </p>
  
  <p>I have this in my <code>zshrc</code> file: 
  <code># Python version from Homebrew
  export PATH="/usr/local/opt/python/libexec/bin:$PATH"</code></p>
  
  <p>When i type <code>which python</code> i get following: <code>/usr/local/opt/python/libexec/bin/python</code></p>
  
  <p>Anyone know how to fix this? Thank you:)</p>