[issue16578] Regular expressions with empty named groups break isname check

[Serhiy Storchaka]

Changes by Serhiy Storchaka <storchaka at gmail.com>:


----------
stage:  -> committed/rejected
superseder:  -> "(?P=)" input for Tools/scripts/redemo.py raises unnhandled exception

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue16578>
_______________________________________