Avoid DeprecationWarning when importing OrderedDict

[kbevers]

in flask_restx/model.py and flask_restx/swagger.py logic is installed to
circumvent differences in Python2 and Python3 when importing from the
collections module. Some classes from collections has been moved to
collections.abc in Python3. OrderedDict is not one of them, hence an
ImportError is raised when trying to import OrderedDict from
collections.abc. This then leads to importing both OrderedDict AND
MutableMapping/Hashable from collections.abc which then raises a
DeprecationWarning since MutableMapping/Hashable lives in
collections.abc in Python3.

This patch should fix those DeprecationWarnings to be raised.

Output from running pytest in a project that uses flask_restx. Here the DeprecationWarnings are seen clearly. I've only fixed the ones pertaining to the Python standard library :

/Users/kevers/miniconda3/envs/webproj/lib/python3.7/site-packages/flask_restx/model.py:12
  /Users/kevers/miniconda3/envs/webproj/lib/python3.7/site-packages/flask_restx/model.py:12: 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 OrderedDict, MutableMapping

/Users/kevers/miniconda3/envs/webproj/lib/python3.7/site-packages/flask_restx/api.py:28
  /Users/kevers/miniconda3/envs/webproj/lib/python3.7/site-packages/flask_restx/api.py:28: DeprecationWarning: The import 'werkzeug.cached_property' is deprecated and will be removed in Werkzeug 1.0. Use 'from werkzeug.utils import cached_property' instead.
    from werkzeug import cached_property

/Users/kevers/miniconda3/envs/webproj/lib/python3.7/site-packages/flask_restx/swagger.py:12
  /Users/kevers/miniconda3/envs/webproj/lib/python3.7/site-packages/flask_restx/swagger.py:12: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from   1 # -*- coding: utf-8 -*-$
'collections.abc' is deprecated, and in 3.8 it will stop working
    from collections import OrderedDict, Hashable

  1 # -*- coding: utf-8 -*-$
-- Docs: https://docs.pytest.org/en/latest/warnings.html

[Colin-b]

Seems like a partial implementation of noirbizarre/flask-restplus#768

[kbevers]

Seems like a partial implementation of noirbizarre/flask-restplus#768

You seem to be correct in that. Applying that patch here would be a better solution.

wiat for applying the noirbizarre/flask-restplus#768

[kbevers]

I went and fixed the rest of the OrderedDict imports as well. Should pose a more complete fix to this.

[SVilgelm]

@ziirish Do we need this or we are going to remove py27 support at all?

[kbevers]

@ziirish Do we need this or we are going to remove py27 support at all?

This is an improvement irregardless of Python2 support. You can't import OrderedDict from collections.abc in either of Python2 or Python3. If you keep the status quo the code will continue to issue DeprecationWarnings. If you enforce Python3 only then you'll have to apply this fix anyway, although there will be other places in the code that also needs a bit of adjusting.

[SVilgelm]

@kbevers thanks for clarification, you are right.

[SVilgelm]

Looks good to me. Thank you

[ziirish]

I'm okay with this change.

Thanks for your contribution!