Update tests with more complete coverage.

lms/djangoapps/bulk_email/models.py

lms/djangoapps/bulk_email/tasks.py

lms/djangoapps/bulk_email/tests/test_email.py

lms/djangoapps/bulk_email/tests/test_err_handling.py

lms/djangoapps/bulk_email/tests/test_models.py

lms/djangoapps/bulk_email/tests/test_tasks.py

lms/djangoapps/courseware/courses.py

lms/djangoapps/courseware/tests/test_courses.py

lms/djangoapps/instructor_task/api_helper.py

lms/djangoapps/instructor_task/subtasks.py

lms/djangoapps/instructor_task/tasks_helper.py

lms/djangoapps/instructor_task/tests/test_api.py

lms/djangoapps/instructor_task/tests/test_tasks.py

lms/djangoapps/instructor_task/tests/test_views.py

lms/djangoapps/instructor_task/views.py

lms/envs/aws.py

lms/envs/common.py