'Unenroll the currently logged-in user, and check that it worked.
`course` is an instance of CourseDescriptor.'

def unenroll(self, course):

    url = reverse('change_enrollment')
    request_data = {'enrollment_action': 'unenroll', 'course_id': course.id.to_deprecated_string()}
    self.assert_request_status_code(200, url, method='POST', data=request_data)
