Pyvista: Better error types

[banesullivan]

We should overhaul all places and error is raised in the API. AssertionError, Exception, and RuntimeError are overused (and inappropriately used):

• AssertionError is raised 47 times
• Exception is raised 49 times
• RuntimeError is raised 56 times

ref https://github.com/pyvista/pyvista/pull/685#pullrequestreview-393235207

[JevinJ]

Quick reference for when to raise the common exceptions, which I think are conventional.

TypeError - When the value is of wrong type, or None if that's not expected.

ValueError - When the value is of the correct type, but wrong value.

AssertionError - Assert should really only be used in testing 99.9% of the time.

RuntimeError - Encountered an error which can not be recovered from.

IOError - Should be rarely used, maybe for a corrupt file.

FileNotFoundError - Self explanatory.

Exception - Almost never, should keep an eye out for this or bare except in try-excepts too.

[banesullivan]

Thanks for that list @JevinJ! It will be helpful to follow those guidelines when fixing this issue

[akaszynski]

@JevinJ please close this if you think we've solved this issue.

[JevinJ]

I forgot about AssertionError and RuntimeErrors, I'll close this and open a PR for the others.