Allow overrides of DJANGO_SETTINGS_MODULE in wsgi.py

[srstsavage]

Set os.environ.setdefault when setting DJANGO_SETTINGS_MODULE in wsgi.py so that other settings modules can be used by setting DJANGO_SETTINGS_MODULE.

[srstsavage]

We probably also want the same behavior for test settings here:

https://github.com/DataONEorg/d1_python/blob/master/gmn/src/d1_gmn/tests/gmn_test_case.py#L44

So

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "d1_gmn.settings_test")

instead of

os.environ["DJANGO_SETTINGS_MODULE"] = "d1_gmn.settings_test"

~~but I can make a separate PR for that.~~

(Added to this PR for simplicity).

[srstsavage]

@rogerdahl Do you think we could get this merged? It's currently blocking our GMN Dockerization effort, and we're hoping not to need to fork the repo for a trivial change.

[mbjones]

Thanks, @srstsavage for putting this together. I'll also ask @iannesbitt and @datadavev to see if they can review and merge this if Roger is off on other adventures.

[srstsavage]

Gentle bump on this one, is this ready for merge or does it need an additional review?

[mbjones]

@iannesbitt or @datadavev can one of you merge this and release a new version of the package to pypi? or let's discuss a path forward on slack.

[srstsavage]

Thank you!