def http_datetime_str_from_dt(dt):
    """Format datetime to HTTP Full Date format.

    Args:
      dt : datetime

        - tz-aware: Used in the formatted string.
        - tz-naive: Assumed to be in UTC.

    Returns:
      str
        The returned format is a is fixed-length subset of that defined by RFC 1123 and
        is
        the preferred format for use in the HTTP Date header. E.g.:

        ``Sat, 02 Jan 1999 03:04:05 GMT``

    See Also:
      - http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3.1

    """
    epoch_seconds = ts_from_dt(dt)
    return email.utils.formatdate(epoch_seconds, localtime=False, usegmt=True)
Format datetime to HTTP Full Date format.

    Args:
      dt : datetime

        - tz-aware: Used in the formatted string.
        - tz-naive: Assumed to be in UTC.

    Returns:
      str
        The returned format is a is fixed-length subset of that defined by RFC 1123 and
        is
        the preferred format for use in the HTTP Date header. E.g.:

        ``Sat, 02 Jan 1999 03:04:05 GMT``

    See Also:
      - http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3.1