Fix regression in symlink to euro-calliope-lib

[timtroendle]

What happened?

The symlink to euro-calliope-lib is not created if it doesn't exist. This leads to failure when trying to create new conda environments.

This used to work and it is a regression, potentially introduced in #331.

Version

1.2.0.dev

Relevant log output

No response

[brynpickering]

I don't quite see how #331 could have introduced this. Its only addition is to delete the symlink if it is invalid. The later line to create the symlink is still there.

[timtroendle]

Agree. In fact, it's #330 that I thought of.

Either way, I am pretty sure this worked just fine when I introduced it in #264 and it now seems broken.

[timtroendle]

Also: This mechanism is quite a hack, anyways. Handling the lib in a separate repo sounds like the cleaner approach that would not require any hacks like this (see #207).