title: Y axis label missing when saving matplotlib file as png
body: <p>I'm trying to save my matplotlib graph as a png. When I run my program, I see the graph appear due to plt.show() and this graph has the y axis label. But then when I go look at the created .png file the y axis label is missing.</p>
  
  <p><a href="https://i.stack.imgur.com/z7k3J.png" rel="nofollow noreferrer">png file</a></p>
  
  <p><a href="https://i.stack.imgur.com/zUw5U.png" rel="nofollow noreferrer">graph</a></p>
  
  <p>Code:</p>
  
  <pre><code>plt.plot_date(times, tps, 'b-', xdate=True)
  
  plt.xlabel('Time', fontsize=20)
  plt.ylabel('Transactions per Second', fontsize=20)
  title = str(sys.argv[1])
  title = title[title.rfind('/') + 1:]
  
  plt.savefig(title + ".png")
  plt.show()
  </code></pre>