ENT-1849: Added caller info to the exception message

Studio export/import can introduce extra spaces into text formatted as code

BOM-1027

guincorn just released its version on 9th-nov-2019 (20.0.0)
and it requires Python 3.x >= 3.4.
so adding constraint < 20.0.0

execute make upgrade

Added caller in to the exception message to debug ENT-1849
Replaced `get_enterprise_learner_data` method call with `enterprise_customer_for_request` to get enterprise customer data from cache or session instead of hitting API.

Revert logs added to investigate audit cert cutoff date

PROD-978

remove small job queue condition for bulk email task

BOM-1012

APIs for XBlock static asset files in Blockstore

Remove View Archived Course button from unfulfilled entitlements.

Fix invocation of (edx.)HtmlUtils.ensureHtml

upgrade edx-enterprise to 2.0.16

Improve navigation on Studio unit page

ENT-2437 | get_enterprise_customer_for_learner method replaced with e…

Bump the version.

Remove View Archived Course button from unfulfilled entitlements
if there is no session availabe to join.

PROD-580

ENT-2437 | get_enterprise_customer_for_learner method replaced with enterprise_customer_for_request.

This reverts commit 31a3a6cb.

[REV-693] Delete old holdback code

Users were awareded audit certificate recently. Adding logs to verify
that cutoff date for awarding certificate is correct

PROD-978

The type of the attrib object wasn't actually a dict.

Add in-context display name editor for units on the course outline.

It was an internal class that we can't easily compare to. So I'm opting
to just make the xml output be more consistent and ordered.  I was
hoping to avoid this since the order shouldn't matter but the juggling
we have to do to validate the unorderd data is more complication than
it's worth.

Improves navigation within Studio for Learning Sequences, speeding up authors who want to see how a learner progresses through content without needing to jump over to the LMS.

This adds a dropdown section navigator to the breadcrumbs on the unit page and copies the sequence navigator from LMS to the studio unit page.

Allow certification regenration for existing honor certificates

staff should be able to regenerate certificates for the students
who have already earned the certificate using honor mode

Prod-612

This is a follow up from MST-16, which was commited
in 3858036a.

Changes:
* Enrich course teams_configuration from a plain Dict
  to a custom XBlock field that uses the new TeamsConfig
  wrapper class.
* Remove teams_conf property from course, as the previous
  change made it redundant.
* Update teams_enabled implementation.
* Remove teams_max_size field from course, which is
  no longer semantically correct, as max team size
  is now defined on a teamset level.
* Remove teams_topics in order to discourage use of raw
  teams config dict.
* Add convenience properties teamsets and teamsets_by_id
  to course.
* Allow periods and spaces in teamset IDs to avoid breaking
  existing course teams.

Some parts of the code still use the old raw config data
(identifiable by searching "cleaned_data_old_format"),
which we expect to be slowly factored away as we build
new teams features. MST-40 has been created to remove any
remaining references if necessary.

MST-18

* fix: bokchoy test

* fix: remove pdb break

Without this the following JS error occurs:

    Uncaught ReferenceError: HtmlUtils is not defined
        at toggleSubmitButton (login:658)