title: Move radial tick labels on a polar plot in matplotlib
body: <p>From <a href="http://matplotlib.org/examples/pylab_examples/polar_demo.html" rel="noreferrer">matplotlib examples</a>:</p>
  
  <pre><code>import numpy as np
  import seaborn as sbs
  import matplotlib.pyplot as plt
  
  r = np.arange(0, 3.0, 0.01)
  theta = 2 * np.pi * r
  
  ax = plt.subplot(111, polar=True)
  ax.plot(theta, r, color='r', linewidth=3)
  ax.set_rmax(2.0)
  ax.grid(True)
  
  ax.set_title("A line plot on a polar axis", va='bottom')
  plt.show()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/iZ1zM.png" alt="polar plot"></p>
  
  <p>How to move the radial tick labels (0.5, 1.0, 1.5, 2.0) to a different angle, say 120 deg?</p>