Motivation
----------
External tools need to know whether or not any test in suite failed. For
example buildbot, or packaging tool would like to stop the execution and
mark it as failed if some tests does not pass.
Modification
------------
Add `--pedantic` switch to tester program which will force it to quit
with non-zero exit code if at least one failure detected. Also update
`tests()` proc in koch to inspect result from tester and propagate it to
user.
Result
------
Nothing has changed in default behaviour. But following invocations will
exit with non-zero code if there failed tests:
./koch tests --pedantic all
./tests/testament/tester --pedantic all
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