title: plt.scatter error 'NoneType' object has no attribute 'sqrt' after running successfully
body: <p>I have a code similar to the one below:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  
  a = [1,2,3]
  b = [3,4,5]
  plt.scatter(a,b)
  plt.grid()
  plt.yscale("linear")
  plt.show()
  </code></pre>
  
  <p>The first couple times I run it, it works fine but afterwards it gives me the error:</p>
  
  <pre><code>'NoneType' object has no attribute 'sqrt'
  </code></pre>
  
  <p>which seems to be located somewhere deep in pyplot rather than it being a problem with my code. Is this something others have encountered? </p>