Compiler errors are now XSI errors.

(cherry picked from commit 21beffd9b260e629c0b3dbb35410a1d388dac217)
avoiding simply returning 'Unknown for every possible error condition.

(cherry picked from commit 6a0f801fef1132aebd119ba3e570c91476d58331)
EmittIng messages according to the severity of the issue. Warnings are now emitted as warnings.
Instead of returning 'Unexpected' we return 'Fail' when a command fails.