title: PyQt5 gets "No module named 'PyQt4'" error calling matplotlib.pyplot in Python 3.5
body: <p>I am using Anaconda with Python 3.5.2, Matplotlib 2.0.2, PyQt5.6 on a windows 10 machine. When I  import matplotlib.pyplot as plt I get the following error:</p>
  
  <pre><code>...
  File "C:...\Anaconda3\Lib\site-packages\matplotlib\backends\qt_compat.py", 
             line 137, in &lt;module&gt; from PyQt4 import QtCore, QtGui
  
  ImportError: No module named 'PyQt4'
  </code></pre>
  
  <p>I don't know why it would want to import from PyQt4 when it has never been installed on my machine. </p>
  
  <p><a href="https://stackoverflow.com/questions/16994232/importerror-no-module-named-pyqt4">This</a> question has the same error, but on a machine that actually has PyQt4 installed. </p>
  
  <p>I have checked my matplotlibrc file, I've used <code>matplotlib.use('qt5agg')</code> in the program, also <code>matplotlib.rcParams['backend'] = "Qt5Agg"</code>. I've uninstalled and reinstalled all the above packages to no avail. I have even attempted to install PyQt4 just to get things going. I'm completely stumped. None of the various possible causes or remedies that I've been able to find on either SO or github have helped.</p>