In the PR https://github.com/edx/edx-platform/pull/10659 the outer_atomic decorator/context manager was created to prevent nested atomic blocks. This method received a boolean parameter read_committed to enforce read-committed MySQL isolation level. From Django 2, the default isolation level Django sets is read-committed, so the aforementioned parameter for outer_atomic can be removed
An @contextmanager will raise an exception from its yield statement if
an exception happens in the with-block that uses it. If the context
manager needs to do clean up, it should do it even if an exception is
raised, so it needs to be done in a finally clause.
A named outer is suitable when dealing with IntegrityErrors. It only
checks that it is not nested under an atomic only if it is nested
under enable_outer_atomic(name=<name>). This way only the view which
is causing IntegrityErrors needs to have its automatic transaction
management disabled and other callers are not effected.
By default, migrations are applied as they always have been. Exporting DISABLE_MIGRATIONS=1 or passing --disable-migrations to Paver commands will create tables directly from apps' models.
