Merge release back to master

Upgrading edx-enterprise to 0.39.8.

EDU-1090, take 2 part 3

Add force_update option to generate_course_overview command

Send welcome email to inactive learners on registration.

LEARNER-2039

This new property knows how to rely on schedule deadliens and fallback to course mode deadlines, when necessary.

This model will be used to control dynamic upgrade deadlines for
learners.

See https://github.com/edx/edx-submissions/pull/68 for details.

EDUCATOR-1090

Revert "Merge pull request #15753 from edx/efischer/submissions_rc"

This reverts commit 95d76568, reversing
changes made to aafd4d9c.

Merge release back to master

https://github.com/edx/edx-enterprise/compare/0.39.7...0.39.8

patch release edx-submissions

patch release edx-submissions

Add advanced settings to generate_courses command

Add forums URL default for docker devstack

Upgrade edx-enterprise package to 0.39.7.

Revert "Add i18n to date in certificate web"

Strip `c` from `.pyc` for error message comparison

Fix attrib check code for library_content import

Attributes come in as a list of dicts with strings as keys and values.
Implicitly casting each result as a tuple causes the code to split the key string into it's characters.
This yields a list of characters, the first two of which are placed into the variables "attr_name" and "attr_value".
This is not only wrong, but because keys tend to be more than 2 characters, the net result is:

"ValueError: too many values to unpack"

Add i18n to date in certificate web

https://github.com/edx/edx-enterprise/compare/0.39.6...0.39.7

In Python 2.7, `__file__` returns `.pyc` by default, this breaks our
comparison so let's strip out the trailing `c`.

Upgrading edx-enterprise to 0.39.6.