Merge pull request #5043 from edx/christina/cohort-selector

common/test/acceptance/tests/discussion/__init__.py

common/test/acceptance/tests/discussion/test_discussion.py

common/test/acceptance/tests/studio/__init__.py

common/test/acceptance/tests/studio/base_studio_test.py

...n/test/acceptance/tests/studio/test_studio_acid_xblock.py

common/test/acceptance/tests/studio/test_studio_bad_data.py

common/test/acceptance/tests/studio/test_studio_container.py

common/test/acceptance/tests/studio/test_studio_general.py

common/test/acceptance/tests/studio/test_studio_outline.py

common/test/acceptance/tests/studio/test_studio_rerun.py

common/test/acceptance/tests/studio/test_studio_settings.py

...on/test/acceptance/tests/studio/test_studio_split_test.py

...acceptance/tests/studio/test_studio_with_ora_component.py