title: Why does argparse not accept "--" as argument?
body: <p>My script takes <code>-d</code>, <code>--delimiter</code> as argument:</p>
  <pre><code>parser.add_argument('-d', '--delimiter')
  </code></pre>
  <p>but when I pass it <code>--</code> as delimiter, it is empty</p>
  <pre><code>script.py --delimiter='--' 
  </code></pre>
  <p>I know <code>--</code> is special in argument/parameter parsing, but I am using it in the form <code>--option='--'</code> and quoted.</p>
  <p>Why does it not work?
  I am using Python 3.7.3</p>
  <p>Here is test code:</p>
  <pre><code>#!/bin/python3
  
  import argparse
  
  parser = argparse.ArgumentParser()
  parser.add_argument('--delimiter')
  parser.add_argument('pattern')
  
  args = parser.parse_args()
  
  print(args.delimiter)
  </code></pre>
  <p>When I run it as <code>script --delimiter=-- AAA</code> it prints empty <code>args.delimiter</code>.</p>