The issue of urllib.quote was discussed at extreme length in issue 3300,
which was specific to Python 3.
http://bugs.python.org/issue3300

In the end, I rewrote the entire family of urllib.quote and unquote
functions; they're now Unicode compliant and accept additional encoding
and errors arguments to handle this.

They were never backported to the 2.x branch; maybe we should do so.
Note that the code is quite different and considerably more complex due
to all the new issues with Unicode strings.