title: rst2pdf : Generate pdf with formulas
body: <p>I need to generate a report with formulas. I found the library rst2pdf. I like to work with the library, but there was a problem when generating pdf with formulas. To generate a formula I use math role. The following code does not work. The error occurs in the module PIL. How to fix it.</p>
  
  <pre class="lang-py prettyprint-override"><code>#!/usr/bin/env python
  # -*- coding: utf-8 -*-
  
  from rst2pdf.createpdf import RstToPdf
  
  mytext = u"""
  ================
  Name of document
  ================
  
  Title
  ---------
  
  ====================  ==========  ==========
  Header row, column 1  Header 2    Header 3
  ====================  ==========  ==========
  body row 1, column 1  column 2    column 3
  body row 2, column 1  column 2    column 3
  body row 3, column 1  column 2    column 3
  ====================  ==========  ==========
  
  :math:`\\frac{1}{\\sigma\\sqrt{2\\pi}}\\exp\\left(-\\frac{(x-\\mu)^2}{2\\sigma^2}\\right) = 123`
  
  """
  
  pdf = RstToPdf()
  pdf.createPdf(text = mytext, output='foo.pdf')
  </code></pre>
  
  <p>Output of the script</p>
  
  <pre class="lang-py prettyprint-override"><code>File "C:\Python27\lib\site-packages\PIL\Image.py", line 1549, in save
      raise KeyError(ext) # unknown extension
  KeyError: '.png'
  </code></pre>