{PERM} and {SCRATCH} expand to "" if not defined

[simondsmart]

What happened?

This is especially dangerous as in the yaml configs {PERM} and {SCRATCH} tend to be used at the start of the various strings, making paths now suddenly relative to the root of the filesystem.

If these environment variables are not defined, this should be an error.

What are the steps to reproduce the bug?

Include a path with {PERM} or {SCRATCH} (or the other env variable substitutions) in any of the .yaml config files.

Version

develop

Platform (OS and architecture)

any

Relevant log output

No response

Accompanying data

No response

Organisation

No response

[corentincarton]

@simondsmart, I implemented a fix in d1956e7.

@colonesej, does that seem reasonable to you or do you see a case where this check would bother us?