'Remove credit requirement status for given username.
Args:
username(str): Username of the user
requirement(CreditRequirement): \'CreditRequirement\' object'

@classmethod
@transaction.atomic
def remove_requirement_status(cls, username, requirement):

    try:
        requirement_status = cls.objects.get(username=username, requirement=requirement)
        requirement_status.delete()
    except cls.DoesNotExist:
        log_msg = u'The    requirement    status    {requirement}    does    not    exist    for    username    {username}.'.format(requirement=requirement, username=username)
        log.error(log_msg)
        return
