Fix Mako templates to use latest request context

Fixed the edX middleware to lazily create request
context for Mako templates, so that it is based on
any changes made to the request object.

Verified that with this fix the "Instructor" tab is
correctly hidden when a staff member is viewing
the course as a student.
Support cohorting students via a CSV File.

TNL-735
add find_fixme task
Updating testing.md for find_fixme
Merge pull request #5961 from edx/dan-f/cohort-csv-upload

Upload CSV file for cohorting students
Merge pull request #6173 from edx/clytwynec/add_find_fixme_method

add find_fixme task
Merge pull request #6189 from edx/andya/fix-masquerade

Fix Mako templates to always use updated request context
Add DEFAULT_FILE_STORAGE configuration.

Tests in common are run with both CMS and LMS configuration (with different env files). Ensure the DEFAULT_FILE_STORAGE variables are in both environments.
Return the filename as returned from default storage's save.

It might be different from the requested filename.
Merge pull request #6215 from edx/christina/test-file-cleanup

Add DEFAULT_FILE_STORAGE configuration.
Adding yaml_config, a new settings module

This reads configuration directly from yaml
and imports it directly into settings
Merge pull request #6188 from edx/jarv/config-refactor-wip

moving defaults for yaml config out of common.py
round-off weight, min_count and drop_count values while returing grading policy
TNL-884
Merge pull request #6092 from edx/zub/bugfix/tnl-884-save-weight-in-gradingpolicy

round-off weight value while returing grading policy
WL-168 When redeeming a Registration Code in the shopping cart, the user should be redirect to the Registration Code Redemption page

fix pep8

updated the failed unit tests

fixed the hover style changes on the redemption page and
 also added a check if the code exists and the user clicks the payment button or billing_details button,
 then we  click the apply code button