title: Python unable to locate mplstyle file in config folder
body: <p>I want to add my custom.mplstyle to matplotlib. However,</p>
  <pre><code>mpl.get_configdir()
  </code></pre>
  <p>returns</p>
  <pre><code>/home/user/.config/matplotlib
  </code></pre>
  <p>In this folder I put the file</p>
  <pre><code>custom.mplstyle
  </code></pre>
  <p>However, when running Python I get</p>
  <pre><code>import matplotlib.pyplot as plt
  plt.style.available
  ['Solarize_Light2', '_classic_test_patch', 'bmh', 'classic', 'dark_background',
   'fast', ..., 'seaborn-talk', 'seaborn-ticks', 'seaborn-white', 'tableau-lorblind10']
  </code></pre>
  <p>but not</p>
  <pre><code>'custom'
  </code></pre>
  <p>When running</p>
  <pre><code>plt.style.use('custom')
  </code></pre>
  <p>I get</p>
  <pre><code>FileNotFoundError: [Errno 2] No such file or directory: 'custom'
  </code></pre>