def METHOD_NAME(datetime):
  """
  Returns timestamp (seconds) by datetime string from ABFS API responses.
  ABFS REST API returns one types of datetime strings:
  * `Thu, 26 Feb 2015 20:42:07 GMT` for Object HEAD requests
    (see http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectHEAD.html);
  """
  # There is chance (depends on platform) to get
  # `'z' is a bad directive in format ...` error (see https://bugs.python.org/issue6641),
  #LOG.debug("%s" %datetime)
  stripped = time.strptime(datetime[:-4], '%a, %d %b %Y %H:%M:%S')
  assert datetime[-4:] == ' GMT', 'Time [%s] is not in GMT.' % datetime
  return int(calendar.timegm(stripped))