title: Matplotlib whole legend leftaligned
body: <p>I would like to align left all the elements of the legend (natively, only the title is left aligned).
  Any idea on how to achieve that?</p>
  
  <p><code>import matplotlib.pyplot as plt, matplotlib 
  _plot = plt.plot(range(5), range(5), label = 'a') 
  legend = plt.legend(loc = 'upper left', title = 'this is a long title')</code></p>