title: how to fix "ImportError: cannot import name 'FormatControl'" for pip?
body: <p>For some reason I can't install anything with pip/pip3 lately. For example, when I try to install mendeley using the command &quot;pip install mendeley&quot;, the following error message appears:</p>
  <pre><code>Traceback (most recent call last):
  File &quot;/Users/u1790509/anaconda3/bin/pip&quot;, line 11, in &lt;module&gt;
    load_entry_point('pip==10.0.1', 'console_scripts', 'pip')()
  File &quot;/Users/u1790509/anaconda3/lib/python3.6/site-packages/pkg_resources/__init__.py&quot;, line 480, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File &quot;/Users/u1790509/anaconda3/lib/python3.6/site-packages/pkg_resources/__init__.py&quot;, line 2691, in load_entry_point
    return ep.load()
  File &quot;/Users/u1790509/anaconda3/lib/python3.6/site-packages/pkg_resources/__init__.py&quot;, line 2322, in load
    return self.resolve()
  File &quot;/Users/u1790509/anaconda3/lib/python3.6/site-packages/pkg_resources/__init__.py&quot;, line 2328, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File &quot;/Users/u1790509/anaconda3/lib/python3.6/site-packages/pip/_internal/__init__.py&quot;, line 42, in &lt;module&gt;
    from pip._internal import cmdoptions
  File &quot;/Users/u1790509/anaconda3/lib/python3.6/site-packages/pip/_internal/cmdoptions.py&quot;, line 16, in &lt;module&gt;
    from pip._internal.index import (
  ImportError: cannot import name 'FormatControl'
  </code></pre>
  <p>The same error appears whenever I attempt to install packages using pip. Does anyone have any suggestion for fixing it?</p>
  <p>thanks,</p>
  <p>Stephen</p>