Enforces a sane UTF-8 encoding for the database connection.

def _CheckConnectionEncoding(cursor):
  """Enforces a sane UTF-8 encoding for the database connection."""
  cur_character_set = _ReadVariable("character_set_connection", cursor)
  if cur_character_set != CHARACTER_SET:
    raise EncodingEnforcementError(
        "Require MySQL character_set_connection of {}, got {}.".format(
            CHARACTER_SET, cur_character_set))