Fix 'makemigrations' and 'migrate' commands

Description

The 'migrate' command complains about "model changes that are not yet
reflected in a migration" and suggests to run "makemigrations". On the
other hand the 'makemigrations' command (mistakenly) generates 2
new migrations that should not really exist.

Two model changes caused this issue:

1) The expiration_datetime field of the CourseMode model from the
course_modes app has been renamed to _expiration_datetime, but kept
inside the "expiration_datetime" column. Thus, this change affects the
model class, but not the SQL structure. It confuses django which
proposes to create a migration that drops the expiration_datetime
column and recreates it. We resolve this issue by making sure the
initial migration and the model agree.

2) The default value of the "mode" field from the CourseRegCodeItem
model has been changed from 'audit' to 'honor'. Again, this change only
affect the model class, but not the SQL structure. Since the "mode"
field was created in the 0002 migration, we only need to patch this
migration to make sure the migration files and the model agree.

Note that this patch does not require users to re-run migrations.

Assignee

Ned Batchelder

Reporter

Open Source Pull Request Bot

Contributor Name

Régis Behmo

Repo

edx/edx-platform

Customer

Epic Link

None

OSCM Assignee

None

Platform Map Area (Levels 1 & 2)

None

Platform Map Area (Levels 3 & 4)

None

Blended Hour Utilization Percentage

None

Priority

Unset
Configure