title: Case-insensitive sections in ConfigParser
body: <p>I am looking at <a href="https://docs.python.org/3.6/library/configparser.html" rel="nofollow noreferrer">Python 3.6 documentation</a> where it says</p>
  
  <blockquote>
    <p>By default, section names are case sensitive but keys are not [1].</p>
  </blockquote>
  
  <p>For the footnote it says</p>
  
  <blockquote>
    <p>[1] (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) Config parsers allow for heavy customization. If you are interested in changing the behaviour outlined by the footnote reference, consult the Customizing Parser Behaviour section.</p>
  </blockquote>
  
  <p>So I look at "14.2.7. Customizing Parser Behaviour" but I cannot find the description of how to make sections case-insensitive.</p>
  
  <p>I want a section like this:</p>
  
  <pre><code>[SETTINGS]
  ...
  </code></pre>
  
  <p>To be accessible like this <code>config['section']</code>, but currently I get an error. This is the only change to the config parser I want to apply.</p>