title: Python3 Replacement for mimetools.choose_boundary()
body: <p>I'm looking at converting a package over to working with Python3 and there's one piece that I'm missing.  According to the Python2 docs <a href="https://docs.python.org/2/library/mimetools.html" rel="nofollow">mimetools</a> has been replaced by <a href="https://docs.python.org/3/library/email.html" rel="nofollow">email</a> in Python3.</p>
  
  <p>However reviewing the <a href="https://docs.python.org/3/library/email.html#differences-from-mimelib" rel="nofollow">differences section</a> of the Python3 docs on email doesn't show a replacement of the chooseboundary() function.  Nor did my Google, SO searches, reading through the docs on the email package turn up anything.</p>
  
  <p>Admittedly the function just returns a string with hostipaddr.uid.pid.timestamp.random, which I can generate myself.  Mainly asking out of curiousity.</p>