Clean other remotes after error.

[hjoliver]

These changes close #4935

If cylc clean fails to clean a remote platform, continue on to other remote platforms but do not clean locally.

@oliver-sanders - you've suggested going further than this #4935 (comment) - but I think that's a potential follow-up. This quick-fix will be a significant improvement as-is - OK?

Requirements check-list

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg and conda-environment.yml.

• Appropriate tests are included (unit and/or functional).
• Already covered by existing tests.
• Does not need tests (why?).

• Appropriate change log entry included.
• No change log entry required (why? e.g. invisible to users).

• (master branch) I have opened a documentation PR at cylc/cylc-doc/pull/XXXX.
• (7.8.x branch) I have updated the documentation in this PR branch.
• No documentation update required.

[oliver-sanders]

you've suggested going further than this #4935 (comment) - but I think that's a potential follow-up. This quick-fix will be a significant improvement as-is - OK?

I don't think #4935 is much of an issue (at least not much of an 8.0.0 issue) so happy with whatever.

(the "broken platform" issue mostly impacts developers and if clean fails it makes little difference to uses how many platforms it cleaned before bailing, either way they are going to have to re-run the command later).

[oliver-sanders]

LGTM; just needs a test.

[hjoliver]

I don't think #4935 is much of an issue (at least not much of an 8.0.0 issue) so happy with whatever.

I agree it's a small issue. #4949 is more important, and this sort of caused that (i.e., a remote clean failure in one workflow prevented cleaning of a bunch of others at the same time). However, it still a bug (cleaning a valid remote should not depend on whether or not we try to clean an invalid one first) and easy to fix.

[hjoliver]

However, as this one is not very important and it's not instantly clear to me how to test it, I'll bump it back to 8.x