Fix track filtering

[jjok]

Fixes #231

I guess these are things that changed with Python 3.

The filter() function now returns a filter object, rather than a list, so it has to be converted to a list before it can be filtered again in the loop.

It seems that a string is iterable, so we need to differentiate between a list and a string, we need to specifically check is values is a list, not just if it is iterable.

[codecov]

Codecov Report

Merging #232 into master will not change coverage.
The diff coverage is 22.22%.

@@           Coverage Diff           @@
##           master     #232   +/-   ##
=======================================
  Coverage   59.92%   59.92%           
=======================================
  Files           9        9           
  Lines         751      751           
=======================================
  Hits          450      450           
  Misses        301      301

Impacted Files	Coverage Δ
mopidy_gmusic/library.py	50.87% <22.22%> (ø)	⬆️

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[jjok]

black run-test: commands[0] | python -m black --check .
would reformat /home/circleci/project/mopidy_gmusic/library.py
Oh no! 💥 💔 💥
1 file would be reformatted, 18 files would be left unchanged.
ERROR: InvocationError for command /home/circleci/project/.tox/black/bin/python -m black --check . (exited with code 1)
___________________________________ summary ____________________________________
ERROR:   black: commands failed

Exited with code exit status 1

@jodal Any idea why Black is failing? Is it some kind of linting that's failing? Or the actual command itself isn't running correctly?
If it's linting, it would be helpful to show what changes should be made, like Flake8 does.

[jodal]

Black does all the changes for you, if you just run black . locally.

[kingosticks]

It's telling you that one file in the codebase failed the formatting check. Just run the command black and it'll make the changes required to the file for you. (don't forget to commit them too)

[jodal]

Thanks :-)