This will leverage the nose attrib plugin to allow us
to break tests apart on our build system to run
in parallel on separate nodes.

There are 3 main changes in this commit:
* CohortFactory now sets up memberships properly, so consuming tests do not
need to explicitly touch CourseUserGroup.users to add() users.
* test_get_cohort_sql_queries has been updated to 3 and 9 queries when using
and not using the cache, respectively. This is needed due to each operation
needing an extra queery to get the CourseUserGroup from the CohortMembership.
* Adding remove_user_from_cohort(), the counterpart to add_user_to_cohort().
This is also to keep tests from touching the users field directly, and keep
CohortMembership data in sync.

Please note that this is a squshed commit and the work of:
Symbolist, macdiesel, nedbat, doctoryes, muzaffaryousaf and muhammad-ammar

This is required so that an a video module exported by one Open edX
deployment and imported by another will work correctly if it contains an
edx_video_id but does not populate other URL fields.

JIRA: MA-110

MA-77 Automatically adds the course id to the videos in VAL
when a course is rerun.

MA-169 Mobile api now calls for mobile_low (default), mobile_high,
 and youtube profiles instead of only mobile_low.

This is needed for courses that license video content where the license
allows only for viewing on the web, not on mobile apps.

JIRA: MA-307

TNL-1253 https://openedx.atlassian.net/browse/TNL-1253

Fix for MA-187 where a value error was thrown when
a course has a video directly under a section. This
PR handles the situations where a chapter or section
can be none, and then returns the appropriate url
if available.

This feature allows upload of video assets to S3. This requires that the
VIDEO_UPLOAD_PIPELINE setting be properly configured and that each
course be configured with a token issued by the media team for their
processing purposes (e.g. linking the video with a YouTube channel).

Co-authored-by: Greg Price <gprice@edx.org>

Move modulestore config for tests to an importable location
Disable pylnt warning for lms imports in common tests
Refactor all testcases that loaded all xml courses
TE-610
TE-489

JIRA: MA-75

Discovered a case I missed on the original version of this. See
https://github.com/edx/edx-platform/pull/5798
JIRA: MA-76

Also fixes checking for mobile_access when course is None
JIRA: MOB-978