WeiDU can exit with return value 0 after encountering errors

[FredrikLindgren]

Continuing a tangential concern from issue #178.

Look into the exception handling and setting of return values. It might just be the parts of the CLI that can exit with failure without setting a return value. --parse-check can fail with a zero return-value if files don't exist, for example. Maybe run the functions called by Main.main wrapped in exception handling?

[dark0dave]

Can we have an exit value and use that for all commands?

[FredrikLindgren]

I think it would depend on the exact circumstances, but unless one of the existing ones would fit better, yes, it might be best to add a new one and use that for the lot.