all versions updates were minor and no visible downgrades

This reverts commit f3161468.

updated the constraints order

- Updating Python Requirements
- Fix cache key generation to use class name and module

This was stringifying the class object directly, resulting in cache keys
like `:1:<class 'xblock_django.models.XBlockConfiguration'>.xblock_django.api.deprecated_xblocks`
which then cause breakage when Django 2.2.13 validates the keys.

Co-authored-by: edX requirements bot <testeng+edx-requirements-bot@edx.org>

Remove pandas requirement.
Replace pandas functionality with itertools.group_by.

* Updating Python Requirements

* Pin django-pipeline and lxml

Co-authored-by: Jeremy Bowman <jbowman@edx.org>

Upgrade uses renamed enterprise catalog endpoints

Also pinned httpretty < 1.0 because that upgrade broke many tests.

Remove duplicate constraints in requirements/constraints.txt uncovered by the recent change in pip-compile output format. I sorted the pinned dependencies by name to try and make it more obvious if this happens again. I also upgraded to pip-tools 4.5.1, which removes the line numbers from the enhanced pip-compile output added in 4.5.0, which should reduce future diff churn and merge conflicts but means that there's a large diff this one last time.

Also unpin edx-search again after the previous change to do that was apparently broken by a merge conflict.

- Reimplement `djcelery.common.respect_language` utility function so we
  can drop the dependency.
- Loosen `celery` pinning to a range, which brings in a fix for a
  possible crash bug

Also, pin `path` to 13.1.0 for now in order to continue supporting py35.

Removing the moto.

This is step 3 of DE-1824.

Also update:
* six 1.13.0 => 1.14.0
* edx-django-utils 2.0.2 => 2.0.3
* skip test that checks all model changes have migrations.  (We defer
  this to step 4.)

Bump django-filter.
Rename the name to field-name.