'Generate a somewhat readable block id unique w/in this course using the category
:param course_blocks: the current list of blocks.
:param category:'

def _generate_block_key(self, course_blocks, category):

    serial = 1
    while True:
        potential_key = BlockKey(category, '{}{}'.format(category, serial))
        if (potential_key not in course_blocks):
            return potential_key
        serial += 1
