title: Python/matplotlib : getting rid of matplotlib.mpl warning
body: <p>I am using matplotlib using python 3.4.
  When I start my program, I have the following warning message:</p>
  
  <blockquote>
    <p>C:\Python34-32bits\lib\site-packages\matplotlib\cbook.py:123:
    MatplotlibDeprecationWarning: The matplotlib.mpl module was deprecated
    in version 1.3. Use <code>import matplotlib as mpl</code> instead.
    warnings.warn(message, mplDeprecation, stacklevel=1)</p>
  </blockquote>
  
  <p>As far as I know I do not use mpl, and all my imports concerning matplotlib are:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  import matplotlib.animation as animation
  </code></pre>
  
  <p>Anything I should do ?</p>