Add asserts to check for 'impossible' NULL values, with comments. In one place where I'n not 1000% sure about the non-NULL, raise a RuntimeError for safety.
Add asserts to check for 'impossible' NULL values, with comments.
In one place where I'n not 1000% sure about the non-NULL, raise
a RuntimeError for safety.

This should fix the klocwork issues that Neal sent me.  If so,
it should be applied to the release25-maint branch also.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator