Accidental (?) implicit dependency on TraitsUI about scimath

[rkern]

We don't generally avoid all traitsui imports in such cases. This is why traitsui has the null backend and is generally careful to avoid actual toolkit imports until someone actually calls .edit_traits().

[andrewcollette]

Thanks @rkern! I will admit to being a little confused here... we recently had a discussion on that consulting project about the value of structuring code to avoid TraitsUI imports for non-GUI things. It looks like, since the model objects use UnitScalar, TraitsUI is unavoidable?

In any case, it looks like the comment in the above file is wrong, as it suggests the import is delayed specifically to avoid loading UI code (which may have been the motivation, but it's not what happens).

[rkern]

I failed to give the fully-nuanced general rules for simplicity's sake (the specific actions you had proposed were perfectly reasonable, so I didn't want to sidetrack). :-) My apologies.

Indeed the comment is bogus. This trait ought to be rewritten as a TraitType with the editor import placed inside of a get_editor() method. This trait predates TraitType, I think.