title: Can't render latex in matplotlib.pyplot in python3
body: <p>While something like <code>matplotlib.pyplot.xlabel(r'Wavelenghth [$\mu$m]')</code> works in  python2 I get error when I use it in python 3</p>
  
  <blockquote>
    <p>TypeError: startswith first arg must be str or a tuple of str, not
    bytes</p>
  </blockquote>
  
  <p>Does anyone know what it the problem? Is it from my latex installation?!</p>