On many buckets, we use s3://bucket/path to separate environments
because AWS used to have a really low limit on the number of buckets
we could have, and we wanted to share them across environments.

If you combine this with an IAM policy that only allows you access
to the s3://bucket/path that you "own", then get_bucket fails.
http://boto.cloudhackers.com/en/stable/ref/s3.html#boto.s3.connection.S3Connection.get_bucket
The HEAD appears to be similar to get_all_keys which requires
ListObjects on the bucket with no conditions.

django-storages (Which is what we write new S3 access in) actually
always passes validate=False unless you're allowing it to create buckets
for you (which we never do).
https://github.com/jschneier/django-storages/blob/1.4.1/storages/backends/s3boto.py#L320-L334

Added course level lang attribute for LMS

added lang attribute to Studio

fixed error when trying to get language attribute on course that does not exist

simplified code

added lang attribure to more places in LMS, added migration for language attribute in course_overview

fixing contraints in the database for language attribute

added lang attribute to several more places in LMS and Studio

added lang attribute to discussion and custom pages; cleaned up code

fixed issue that was causing test failures

moved lang attribute higher in tree in two places

EDUCATOR-563

EDUCATOR-396

https://openedx.atlassian.net/browse/EDUCATOR-393

This reverts commit f97f0525, reversing
changes made to 800bcd8e.

EDUCATOR-390 and EDUCATOR-391 | Send GRADING_POLICY_CHANGED signal when something changes the grading policy.

https://openedx.atlassian.net/browse/EDUCATOR-389

This makes it possible to refer to multiple book from a single app.

This also means that Open edX branches will be able to pass bok-choy
tests (at least if the books have already been built.)

This reverts commit 1224e341. I've also added
NotImplementedPartitionScheme, which allows deprecated partition types to have
a valid entry point despite being unusable.

TNL-6675

TNL-6743

incoming scores.

TNL-6697

Re-running a course now clones the OrganizationCourse and RestrictedCourse data from the old run to the new run. This will allow administrators to avoid the tedium of manually recreating this data.

TNL-6746

TNL-6744

TNL-6674