title: Error after upgrading pip: cannot import name 'main'
body: <p>Whenever I am trying to install any package using pip, I am getting this import error:</p>
  
  <pre><code>guru@guru-notebook:~$ pip3 install numpy
  Traceback (most recent call last):
    File "/usr/bin/pip3", line 9, in &lt;module&gt;
      from pip import main
  ImportError: cannot import name 'main'
  </code></pre>
  
  <p><br></p>
  
  <pre><code>guru@guru-notebook:~$ cat `which pip3`
  #!/usr/bin/python3
  # GENERATED BY DEBIAN
  
  import sys
  
  # Run the main entry point, similarly to how setuptools does it, but because
  # we didn't install the actual entry point from setup.py, don't use the
  # pkg_resources API.
  from pip import main
  if __name__ == '__main__':
      sys.exit(main())
  </code></pre>
  
  <p>It was working fine earlier, I am not sure why it is throwing this error.
  I have searched about this error, but can't find anything to fix it.</p>
  
  <p>Please let me know if you need any further detail, I will update my question.</p>