DeprecationWarning in flask.sessions

[tirkarthi]

flask.session imports MutableMapping from collections which is deprecated in Python 3.7 and will be removed in 3.8. For some reason since there are similar warnings in other libraries like werkzeug and jinja that are fixed seems to hide this warning. Importing session directly from flask folder causes this warning

Expected Behavior

DeprecationWarning should not be shown since it causes incompatibility with 3.8

Actual Behavior

Tell us what happens instead.

Python 3.8.0a0 (heads/master:78de01198b, Dec 29 2018, 11:36:21)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import warnings
>>> warnings.filterwarnings("default", category=DeprecationWarning)
>>> import sessions
/home/karthi/flask/flask/sessions.py:14: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated, and in 3.8 it will stop working
  from collections import MutableMapping

Environment

• Python version: Python 3.8.0a0
• Flask version: 1.1dev
• Werkzeug version: 0.14

Upstream PR : python/cpython#10596

[tirkarthi]

@davidism I am closing this since the PR #3054 was merged into 1.0-maintenance branch. Feel free to reopen this if I am wrong.