Code review comment for lp:~mbp/bzr/test-errors

    def test_mutter_never_fails(self):
        # Even if the decode/encode stage fails, mutter should not
        # raise an exception
        # This test checks that mutter doesn't fail; the current behaviour
        # is that it doesn't fail *and writes non-utf8*.
        mutter(u'Writing a greek mu (\xb5) works in a unicode string')
        mutter('But fails in an ascii string \xb5')
        mutter('and in an ascii argument: %s', '\xb5')
        log = self.get_log()
        self.assertContainsRe(log, 'Writing a greek mu')
        self.assertContainsRe(log, "But fails in an ascii string")
        # However, the log content object does unicode replacement on reading
        # to let it get unicode back where good data has been written. So we
        # have to do a replaceent here as well.
        self.assertContainsRe(log, "ascii argument: \xb5".decode('utf8',
            'replace'))

So, this test is passing in the way the comment describes: mutter
doesn't actually fail, but we're no longer writing what we expected
to.

Looking at what got written, it's consistent with the currently
documented behaviour: lines sent as unicode get written as utf8 and
lines sent as byte strings are sent through as such (therefore the
file's then not valid utf8.) I think this is still reasonable
behaviour.

(Pdb) p log
'0.232 Writing a greek mu (\xc2\xb5) works in a unicode string\n0.232
 But fails in an ascii string \xb5\n0.232 and in an ascii argument:
\xb5\n'

The main change we'd need then, is that when looking at the result, we
should just search for a non-utf8 string.