I was running "make suspicious" in Doc/ and this was the output after finding 3 suspicious markups:

 writing output... [ 52%] library/inspect
 WARNING: [library/inspect:437] ":int" found in ">>> def foo(a, *, b:int, **kwargs):"
 WARNING: [library/inspect:437] ":int" found in "'(a, *, b:int, **kwargs)'"
 WARNING: [library/inspect:437] ":int" found in "'b:int'"
 writing output... [100%] whatsnew/index
 build finished with problems, 3 warnings.
 make: *** [build] Error 1

After figuring out how to mark these as false positives and adding the relevant entries to susp-ignored.csv, I ran "make suspicious" again, and got this useful message at the end:

 writing output... [100%] whatsnew/index
 build succeeded.

 Suspicious check complete; look for any errors in the above output or in build/suspicious /suspicious.csv.  If all issues are false positives, append that file to tools/sphinxext/susp-ignored.csv.

The problem is that this message should be displayed when there are failures, but it's not.

Attached an attempt to fix the Makefile to avoid exiting in case of failures when the builder is "suspicious".  Given that I'm not really familiar with makefiles, it probably doesn't make much sense.