Add new deprecation warning classes for RBTools 5 and 6.
Review Request #12523 — Created Aug. 9, 2022 and submitted
which will be used for upcoming changes that deprecate some older
RemovedInRBTools40Warningwill remain in the codebase until all
pending deprecations for 4.0 have been removed.
This also introduces the first usage of Python type hints to our
codebase. This is new for us, so we'll need to develop best practices
Made use of this in an in-progress change.
Unit tests pass.