comms.http._decide_encoding sometimes gives a warning like WARNING: Unknown or invalid encoding 'ISO-8859-1,utf-8;q=0.7,*;q=0.7' and returns None because encodings detection fails but it could detect encoding easily because 'ISO-8859-1,utf-8;q=0.7,*;q=0.7'` contains multiple encodings separated by comma and with quality factor which is 1 by default. The given string has the following encodings:

1. ISO-8859-1 (quality 1.0)
2. utf-8 (quality 0.7)
3. * = wildcard for other encodings (quality 0.7)