It now has slightly better rationale and a less awkward wording in the
explanation.

Inspired by a report of a neither/or conflict by 'animalize' on docs@.

and ASCII letter now raise a deprecation warning and will be forbidden in
Python 3.6.

conditional group references are used in lookbehind assertions in regular
expressions.

work in lookbehind assertions in regular expressions.

raises a warning.  Patterns that can only match empty strings are now
rejected.

re.ASCII. It was newer worked.

and re.subn().

Also, improve variable names and fix column numbers
in the generated output.

which anchor the pattern at both ends of the string to match.

Original patch by Matthew Barnett.

pattern at both ends of the string to match.

Patch by Matthew Barnett.
Closes #16203.

Patch by Serhiy Storchaka.

Closes #14250: regex.flags has not only explicit flags but also implicit flags and those from the pattern