Add warning when dropping inclusion inherent (#2261)

* Add warning when dropping inclusion inherent

* improve warning when dropping inclusion inherent

- use the actual runtime `warn!` macro
- do not speculate about why the error occurred
- show the actual error returned

* BROKEN: add note if the current block matches the session start block

This doesn't compile for a variety of reasons; this commit demonstrates
what the issues are. I don't think this is an essential feature, so I'm
stopping work on it here instead of pushing through it.

* Revert "BROKEN: add note if the current block matches the session start block"

This reverts commit eeb79ab7.

* ensure a runtime logger exists before attempting to log a warning to it