code: def http_get_metadata(metadata_path, timeout=__HTTP_DEFAULT_TIMEOUT_SEC):
    
    metadata_path = __METADATA_PREFIX + metadata_path
    try:
      response = urllib2.urlopen(metadata_path, None, timeout)
      if response.getcode() != 200:
        raise IOError("Non-200 response " + str(response.getcode()) + " reading " + metadata_path)
      return response.read()
    except urllib2.URLError as error:
      raise IOError("URLError in http_get_metadata: " + repr(error))
docs: Fetch AWS metadata from http://169.254.169.254/latest/meta-data/<metadata_path>
    ARGS:
      metadata_path - the optional path and required key to the EC2 metadata (e.g. "instance-id")
    RETURN:
      response content on success
    RAISE:
      URLError if there was a problem reading metadata