Allow cylc clean to work with --force when DB is corrupted/incompatible

[MetRonnie]

Describe exactly what you would like to see in an upcoming release

Instead of

$ cylc clean temp5 --force
ServiceFileError: Cannot clean - Workflow database is incompatible with Cylc 8.0b3.dev, or is corrupted

we should be able to use --force to force it to clean, possibly with a message similar to when there is no DB, .e.g

INFO - Workflow database is incompatible with Cylc 8.0b3.dev, or is corrupted - will only clean locally

Pull requests welcome!

[MetRonnie]

Marking as a question to bring up on Friday in case there is a reason not to do this

[oliver-sanders]

Low priority.

[MetRonnie]

Every now and then I run into this, which is a bit frustrating. I'd be tempted to promote this to 8.0.0 or rc2

[oliver-sanders]

How are you getting corrupted DBs?

[MetRonnie]

Not so much corrupted DBs as trying to clean Cylc 7 runs

[oliver-sanders]

Ah, do we not prohibit cleaning Cylc 7 runs?!

[oliver-sanders]

For a Cylc 7 workflow you get:

Workflow database is incompatible with Cylc 8.0rc1.dev, or is corrupted

Which is fine. I don't think cylc clean should attempt to remove Cylc 7 workflows, users should continue to use rose suite-clean (which has remote support) or employ whatever local practices they usually use.

We could detect a Cylc 7 workflow and print this advice for clarity?