First group of the `test_cancellation.py` `run_in_actor` removal
(#477),
- `test_remote_error` -> blocking `to_actor.run()` (single erroring
one-shot; a bad-arg `TypeError` still relays as a
`RemoteActorError`).
- `test_multierror` -> concurrent fan-out via
`gather_contexts([p.open_context(assert_err_ctx) ...])` over
`start_actor()` portals. NB `gather_contexts` is cancel-on-first
so the 2nd errorer is usually cancelled before relaying its own
exc and the pair collapses to a single `RemoteActorError` (vs the
legacy reap-all-at-teardown `BEG`-of-N) — the assertion now
accepts either shape.
- delete `test_multierror_fast_nursery` — a 25-actor stress test of
`run_in_actor`'s teardown-reap; no analogous surface under the
`to_actor` fan-out.
- add an `assert_err_ctx` `@context` shim for the `open_context`
fan-out.
Remaining `test_cancellation` groups (some_cancels_all, nested,
SIGINT, sync-blocking) still on `run_in_actor` — ported next.
(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
Gud Boi
ba4af0ad1a