The `absubmit` plugin for beets has no respective plugin test that
is named after the default plugin test schema defined in `common.nix` [1],
so not explicitly declaring that the plugin has *no tests* (i.e. the
respective test list is empty), `mkPlugin` will try to disable the
non-existant test `test/test_absubmit.py`), breaking beet's build.
[1]: c7916a507b/pkgs/tools/audio/beets/common.nix (L39)
Highlights:
* We now have a beets-unstable
* We now run tests for beets-minimal
* We're much more strict about the effects of enabling/disabling plugins
* All patches but one were dropped
* Removal of deprecated nose in favor of pytest
* Art resizing is working better now
