By default, disable all caching in tests, to preserve test independence.
In order to enable caching, inherit from CacheSetupMixin, and specify
which cache configuration is needed.

[EV-32]

More accurately, this creates a 4th shard because the
last shard is always the default.

More accurately, this creates a 4th shard because the
last shard is always the default.

There's no need to use a string literal in setattr, delattr, or the
two-argument form of getattr.

Please note that this is a squshed commit and the work of:
Symbolist, macdiesel, nedbat, doctoryes, muzaffaryousaf and muhammad-ammar

The old line:

    from path import path

produced pylint errors because of the baroque way that path.py defined
"path".  We tried to get them to change how they defined it, but they
deleted the name instead: https://github.com/jaraco/path.py/issues/102

(Jason then changed his mind, but this is a better way to use path.py,
it avoids the pylint error at least.)

* Add new role for support staff.
* Move dashboard/support functionality into a new Django app called "support".
* Add support view for searching and regenerating certificates.
* Refactor certificates views into separate files.

only require ccx-keys once

get_current_ccx will now expect a CourseKey instance as its argument, and will raise a value error if this expectation is not met.

document reason for local import

add special methods to pass attribute setting and deletion through to the wrapped modulestore

add __setattr__ and __delattr__ per code review, update __init__ to work with new methods

style change per code review

clean up context manager usage as recommended by code review

remove unused code and imports

convert modulestore type tests to use the `get_modulestore_type` api, remove unused imports

code quality: add docstrings

increase coverage for utils tests

fix bug found in testing.

increase test coverage on modulestore wrapper

code quality fixes

code-quality: ignore import error, but mark site for future consideration

remove references to middleware that were missed previously

use key apis rather than local implementation of key conversion.  remove local implementationa

remove spurious test for attribute

fix test setUp to avoid unneeded flattening

code quality fixes

add security check ensuring that the coach is coach for *this* CCX.

prevent ccx/deprecated course id problems

1.  do not allow ccx objects to be created if the course id is deprecated
2.  filter out any ccx memberships that involve deprecated course ids (in case there are bad ccxs in the database)

Fix test failures and errors arising from incorrect code path execution

Create context manager to handle unwrapping and restoring ccx values for the modulestore wrapper, employ it throughout modulestore wrapper implementation

Update edx-lint to the version that checks if tearDown uses super.

Convert a number of tearDown methods into addCleanup.

Remove some unneeded tearDown methods: no need to call patch.stopall if
none of them were started with patch.start.

The existing pattern of using `override_settings(MODULESTORE=...)` prevented
us from having more than one layer of subclassing in modulestore tests.

In a structure like:

    @override_settings(MODULESTORE=store_a)
    class BaseTestCase(ModuleStoreTestCase):
        def setUp(self):
            # use store

    @override_settings(MODULESTORE=store_b)
    class ChildTestCase(BaseTestCase):
        def setUp(self):
            # use store

In this case, the store actions performed in `BaseTestCase` on behalf of
`ChildTestCase` would still use `store_a`, even though the `ChildTestCase`
had specified to use `store_b`. This is because the `override_settings`
decorator would be the innermost wrapper around the `BaseTestCase.setUp` method,
no matter what `ChildTestCase` does.

To remedy this, we move the call to `override_settings` into the
`ModuleStoreTestCase.setUp` method, and use a cleanup to remove the override.
Subclasses can just defined the `MODULESTORE` class attribute to specify which
modulestore to use _for the entire `setUp` chain_.

[PLAT-419]

These were found by the new pylint checker I wrote! :)