> An easier hack is likely just a new "always run in subprocess" container
> with submodule names in regrtest.py. It's not elegant, but it will work.
>

True, that's also an option. I had it in mind in the beginning, but it's
too hacky for my tastes :-) Not doing state-changing stuff in the global
scope is a good practice anyway, so the restriction should be too horrible.

Do we have some sort of conventions of outside-discoverable module
attributes (like the __REGRTEST_SUBPROCESS__ proposed above)? I.e. in terms
of naming, type, expected values?