Some status strings were accidentally tuples thanks to stray commas, and
ugettext raised an exception as a result.

JIRA: MA-323

TNL-1185

TNL-1146

TNL-1146

TNL-1380

Since we began monkey-patching `django.utils.translation` [1], we no
longer need to check for empty strings before translating them.
Previously, the empty string would be translated into translation
metadata. Now, translating the empty string intuitively yields the empty
string.

[1] 86633df3

get the raw DescriptorSystem, not the CombinedSystem when instantiating xmodules (TNL-1226)

quality fixes

remove trailing comma

The existing pattern of using `override_settings(MODULESTORE=...)` prevented
us from having more than one layer of subclassing in modulestore tests.

In a structure like:

    @override_settings(MODULESTORE=store_a)
    class BaseTestCase(ModuleStoreTestCase):
        def setUp(self):
            # use store

    @override_settings(MODULESTORE=store_b)
    class ChildTestCase(BaseTestCase):
        def setUp(self):
            # use store

In this case, the store actions performed in `BaseTestCase` on behalf of
`ChildTestCase` would still use `store_a`, even though the `ChildTestCase`
had specified to use `store_b`. This is because the `override_settings`
decorator would be the innermost wrapper around the `BaseTestCase.setUp` method,
no matter what `ChildTestCase` does.

To remedy this, we move the call to `override_settings` into the
`ModuleStoreTestCase.setUp` method, and use a cleanup to remove the override.
Subclasses can just defined the `MODULESTORE` class attribute to specify which
modulestore to use _for the entire `setUp` chain_.

[PLAT-419]

These were found by the new pylint checker I wrote! :)

This provides a better UX for video uploaders, because recent uploads
are readily visible at the beginning of the table.

This fixes two bugs:
1. All statuses were listed as "Unknown"
2. Non-ASCII characters in a header column translation resulted in a 500

TNL-935

This fixes two bugs:
1. All statuses were listed as "Unknown"
2. Non-ASCII characters in a header column translation resulted in a 500

Fix i18n for video status strings (broken in commit 4b53f4df) and remove
unnecessary complexity from a test case. This also removes the status
whitelist in the video upload configuration. Because status is included
in the CSV report, it is not necessary to filter the included videos by
status.

returns XBlockuser with 2 data layers

TNL-935

Possibly caused by a bad merge.

TNL-652

Co-Authored-By: Christina Roberts <christina@edx.org>
Co-Authored-By: Daniel Friedman <dfriedman@edx.org>
Co-Authored-By: Don Mitchell <dmitchell@edx.org>

Co-Authored-By: Jean-Michel Claus <jmc@edx.org>
Co-Authored-By: Brian Talbot <btalbot@edx.org>
Co-Authored-By: Tim Babych <tim@edx.org>
Co-Authored-By: Oleg Marshev <oleg@edx.org>
Co-Authored-By: Chris Rodriguez <crodriguez@edx.org>