Flask-RESTful will fail when Flask deprecates propagate_exceptions: Fix

[transreductionist]

Handle the deprecation of Flask's propagate_exceptions

Overview of the Issue in Flask-RESTful

Flasks app.propagate_exceptions will be deprecated in the next release, and although the Flask developers don't have a release date, given their release history it may be sooner rather than later. If it is deprecated Flask-RESTful will throw an exception in flask_restul.__init__ in the handle_errors method. This is the only place in Flask-RESTful where this
attribute is accessed.

This pull request addresses the need to fix this issue in Flask-RESTful. Along with the fix I cleaned up that area of the code a bit, and made a few minor style changes, e.g., fixing a typo, removing an extra line feed, etc. Unit tests were added and pass.

Currently in Flask, if app.propagate_exceptions is set to True then the exceptions are re-raised rather than being handled by the app’s error handlers. When app.propagate_exceptions is deprecated app.config['PROPAGATE_EXCEPTIONS'] may be used in its place. Additionally, if app.propagate_exceptions is None (default value), then a sensible value should be substituted.

Relevant Flask Documentation

Flask Config Docs

Relevant Flask Pull Requests

#4716: deprecate most config attributes (fixed by #4722)
#4722: deprecate most config attributes (merged)

[transreductionist]

Looking at Flask 2.3 the propagate_exceptions method, which chose a sensible value if the propagate_exceptions is None, has been removed (deprecated). Handling the case where propagate_exceptions is None has been included here.

[joshfriend]

well that was an adventure... there's no CI for the project anymore because Travis CI went non-free a long time ago, trying to run tests doesn't work well anymore because none of the python versions in the project setup support Apple M1/M2 macs, and setuptools no longer supports pypi publishing (so i had to hack it with twine).