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
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