py3: fix non-ASCII URLs - decode unicode correctly before passing them to controllers as unicode strings

This is needed for supporting localized repo path names in the path of URLs.

Some references:

https://www.python.org/dev/peps/pep-0333/#unicode-issues
https://bugs.python.org/issue16679
http://lucumr.pocoo.org/2010/5/25/wsgi-on-python-3/
https://bugs.launchpad.net/pecan/+bug/1451842
https://github.com/tipabu/eventlet/commit/a5a7751b013fe99b6d30acbca79e819770e9ae5d