As @gregory.p.smith noted in GitHub [0] this fixes only protocol level bugs. There are some parsing ambiguities in urllib that are potential security issues still to be fixed.

issue20271 - urllib.urlparse('http://benign.com\[attacker.com]') returns attacker.com as hostname . A slightly related issue https://bugs.python.org/issue20271
issue35748 - urllib.urlparse(r'http://spam\eggs!cheese&aardvark@evil.com') returns evil.com as hostname
issue23505 - Urlparse insufficient validation leads to open redirect
issue33661 - urllib may leak sensitive HTTP headers to a third-party web site (Redirecting from https to http might also pass some headers in plain text. This behavior was changed in requests, golang, Curl that had their own respective CVEs)

As a fun side note this vulnerability was used by one of our own tests as a feature from 2012 to test another security issue (issue14001) [1] :) 

[0] https://github.com/python/cpython/pull/12755#issuecomment-481599611
[1] https://github.com/python/cpython/pull/12755#issuecomment-481618741