And canonicalise file paths, so that output is consistent, even in
out-of-tree builds.
Capturing stderr output produces better diagnostics.
Diagnostics for 32705.
When practracker is disabled, its output will be empty. We don't
want that happening during our tests.
Fixes bug 32705; bugfix on 0.4.2.1-alpha, when test_practracker.sh
was introduced.
This test runs practracker with a set of 0 thresholds, to make sure
that it enumerates all its values right. It tries running with an
empty exceptions file, and with an exceptions file that covers
_some_ of the data, and it makes sure that the outputs are as expected.
