* fix: upgrade py2neo from 3.1.2 to 2021.1.5
The dump_to_neo4j management command has not been working
since the upgrade to python 3.8. The latest version of
python that py2neo 3.1.2 states support for is python 3.5,
so this isn't surprising.
The earliest non-prerelease version of py2neo that supports
python 3.8 is 2020.x (skipping the 4.x and 5.x series). Since
we're going as far as a 2020.x, we may as well upgrade all the
way to the newest series, 2021.x. This commit does that upgrade,
as well as a handful of minor code modifications in order
to handle breaking changes that have been made to the py2neo
API, and some unrelated pin bumps as the result of
'make upgrade'.
This will also require an upgrade of Coursegraph's Neo4j
version from 3.2.x to 3.5.x.
TNL-8386
This method from the toggle legacy classes should not actually be
exposed to all. So we get rid of it by manually setting the cached
value. While we are at it, we convert the STORAGE_BACKING_FOR_CACHE
legacy waffle switch to its modern version. As the flag is not being
used elsewhere, this should not break anything.
We take the opportunity to modernize waffle switches from
block_structure.config: to do so we convert the INVALIDATE_CACHE_ON_PUBLISH and
RAISE_ERROR_WHEN_NOT_FOUND waffle switches from legacy classes to their modern
equivalents. These switches are not used outside of edx-platform, so this
change should not trigger any error.
Also
* Instead of caching when a course is last published, we get this information
from the CourseStructure table
* This commit introduces a mock py2neo Graph to be used for testing
