title: python networkx import error: cannot import name release
body: <p>I'm on macOS, using another program needs to run python script contains networkx module. My networkx2.1 is installed using:</p>
  
  <pre><code>pip install networkx --user
  </code></pre>
  
  <p>The error raised is that:</p>
  
  <pre><code>File "/Users/myname/Library/Python/2.7/lib/python/site-packages/networkx/__init__.py", line 43, in &lt;module&gt;
  import networkx as nx
  ImportError
  from networkx import release
  cannot import name release
  </code></pre>
  
  <p>I've done some search on this error, and those seem working is by using the networkx of another version, or install/uninstall. </p>
  
  <p>I've already tried uninstall and reinstall networkx of version 1.9, 1.5, 1.1, however this error continues.</p>
  
  <p>Anyone also encounterd this issue?</p>