docs: 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)