Not compatible with mopidy v3

compat as well as other things were removed with v3 of mopidy. v3 is not compatible with python 2.

https://dev.funkwhale.audio/funkwhale/mopidy/-/blob/master/mopidy_funkwhale/commands.py#L1

A workaround is to install mopidy v2.2.3 with python 2

sudo -H pip2.7 install git+https://github.com/mopidy/mopidy.git@v2.2.3