Avoid clobbering already configured path

[findepi]

Almost fixes #2956

[findepi]

@kiview should i rebase?

[findepi]

No conflicts yet, ready for review.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you believe this is a mistake, please reply to this comment to keep it open. If there isn't one already, a PR to fix or at least reproduce the problem in a test case will always help us get back on track to tackle this.

[findepi]

.

[rnorth]

So this will fail fast, rather than allow the user to do something which is known to be broken (#2956)?

I think this is fair for now, to reduce user confusion. We'll need to revisit #2956 later to actually fix the behaviour.

[kiview]

Thanks for the improvement @findepi.

@rnorth I agree, this should be fixed eventually, but this PR already improves the UX and does not add much complexity, so it's fine to add this for now.