Use string formatting

[fabaff]

For the URLs use string formatting, {}.format(string).

url = (
            scheme + '://' + host + '/gwr/gop.php?cmd=GWRBatch&data=<gwrcmds><gwrcmd><gcmd>RoomGetCarousel</gcmd><gdata><gip><version>1</version><token>' + token + '</token><fields>name,status</fields></gip></gdata></gwrcmd></gwrcmds>&fmt=xml')

This will help to avoid the TypeErrors mentioned in home-assistant/core#11983