[PATCH 0 of 2] tests: hghave || exit 80

[Nicolas Dumazet]

Hello!

We use in several tests "hghave $feature || exit 80" to check for avaibility
of $feature before running a test: hghave exits with exitcode 0 only if
$feature is availabe. If $feature is not available, hghave exits with 
exitcode 1, which causes the test to exit with exitcode 80; and then run-tests 
checks the test exitcode to show a "skipped" message.

If, however, "hghave $feature" crashes (Traceback, caused for example by
a SyntaxError) it exits with exitcode 1, which in its turns exits the test with
errorcode 80... and run-tests prints happily a "test-skipped" message instead
of detecting a failure.

I have included two patches to avoid those issues:
* The first one makes sure that all hghave targets are crash-free
* The second one catches errors when hghave fails inside a test, to mark the
  test as failed.

Those two patches might look overlapping, but both are necessary:

1) when all hghave targets are tested for validity, a single test cannot 
   indeed fail on a hghave call. However if one introduces an error in, 
   say inotify, he will want test-inotify* tests to run (no skips), 
   and will want them to fail: one should not have to run test-hghave to 
   detect an error outside of hghave scope.
2) Simetrically, it is not because all individual tests calling hghave
   run correctly that all hghave targets are correct.


Regards,

Nicolas.