facebook/tornado — pull request #454 by minrk (2012-02-02 22:12:00+00:00)
Title: coerce kwarg keys to str

If handler regex is unicode, the keys of groupdict are unicode, but should be
str, as Python < 2.6.5 does not accept unicode keys in:

_execute(*args, **kwargs)

Since they are for keyword args, they will be valid identifiers, and thus ascii.