LMS-2947 remove get_error_courses in Split.

...angoapps/contentstore/management/commands/clone_course.py

...ngoapps/contentstore/management/commands/delete_course.py

cms/djangoapps/contentstore/management/commands/import.py

cms/djangoapps/contentstore/tests/test_contentstore.py

cms/djangoapps/contentstore/tests/test_course_listing.py

cms/djangoapps/contentstore/tests/test_crud.py

cms/djangoapps/contentstore/tests/test_users_default_role.py

cms/djangoapps/contentstore/utils.py

cms/djangoapps/contentstore/views/tabs.py

common/djangoapps/student/tests/test_course_listing.py

common/lib/xmodule/xmodule/modulestore/__init__.py

common/lib/xmodule/xmodule/modulestore/mixed.py

common/lib/xmodule/xmodule/modulestore/mongo/base.py

common/lib/xmodule/xmodule/modulestore/mongo/draft.py

common/lib/xmodule/xmodule/modulestore/split_mongo/split.py

common/lib/xmodule/xmodule/modulestore/store_utilities.py

...ashboard/management/commands/tests/test_git_add_course.py

lms/djangoapps/dashboard/sysadmin.py