Add "python_warnings_as_errors" flag
When !172 (merged) is merged, all warnings are now handled via the "warnings" library. This will allow us to perform a similar operation as "-Werror" by informing the warnings module to turn warnings into errors: https://docs.python.org/3/library/warnings.html#the-warnings-filter
Add new flag to do so
Suggested by @john.parent
Edited by Joe Snyder