failing second iteration not reflected by status code

[klbostee]

Replacing "sum" by (the non-existing function name) "summ" in "reducer1" in "examples/itertwice.py" and then running "bin/test" leads to 1 failure and 1 error, whereas doing the same change in "reducer2" (and removing "reducer2" as combiner for the first iteration) leads to 0 failures and 1 error.

[klbostee]

Actually, this probably is due to combiners. When the reducer is used as a combiner the error happens earlier in the UNIX pipeline command and consequently doesn't trigger a nonzero status code.