title: How to prevent "ImportError: No module named oauth2client.client" on Google App Engine?
body: <p>We are receiving an error:</p>
  
  <blockquote>
    <p>ImportError: No module named OAuth2Client</p>
  </blockquote>
  
  <p>We have noticed scores of questions around this topic, many unanswered and at least one answer that describes the solution of copying over files from the Google App Engine SDK. </p>
  
  <p>This approach, however, seems tedious because all the dependencies are unclear. If we copy over <code>oauth2client</code> then run, the next error is another module that is missing. Fix that, then another module is missing, etc., etc. </p>
  
  <p>What is ironic is that we can see all the files and modules needed, listed from Google App Engine SDK right in PyCharm but they seem inaccessible to the script.</p>
  
  <p>Is there no better way to pull in all the files that <code>oauth2client</code> needs for Python to work on App Engine? </p>