It took me awhile to figure out how to run this command, as the documentation is incorrect (rake command has not been updated for name change from clone to clone_course). I know it is unrelated, but can you update the doc also? The course you are cloning into (in this case, edx/111/foo) must already have been created and must be empty.

./manage.py cms clone_course --settings=dev master/300/cough edx/111/foo