`AdvancedSubtensor` will call out to Python (i.e. Numba's object mode), because
that's not currently supported in nopython mode.  This causes problems with
indices that contain slices, because Numba has its own internal representation
of slices and no unboxing for that (i.e. conversion back to Python).

Also check exception messages in the tests.

The "tests.*" exclusion only excludes test subpackages from being
installed, while "tests" itself is still installed.  List it explicitly
to exclude it as well.