skipped tests

[Chadys]

Some tests are not being run any more. From the CI log:

tests/test_backends.py::TestTokenBackend::test_decode_with_no_expiry[title0-backend0] SKIPPED [ 52%]
tests/test_backends.py::TestTokenBackend::test_decode_with_no_expiry_no_verify[title0-backend0] SKIPPED [ 52%]
tests/test_backends.py::TestTokenBackend::test_decode_with_expiry[title0-backend0] SKIPPED [ 53%]
tests/test_backends.py::TestTokenBackend::test_decode_with_invalid_sig[title0-backend0] SKIPPED [ 54%]
tests/test_backends.py::TestTokenBackend::test_decode_with_invalid_sig_no_verify[title0-backend0] SKIPPED [ 54%]
tests/test_backends.py::TestTokenBackend::test_decode_success[title0-backend0] SKIPPED [ 55%]

When you look at the details, you get Skipped: got empty parameter set for (title, backend). I think that's because in the parametrize, you do for backend in backends but backends is never set, only self.backends is

[Chadys]

Also, if you fix this, you'll need to look at jazzband#963 because otherwise those tests will fail once activated back