Try to stop failing tests as late as possible on OSX.
* bzrlib/tests/blackbox/test_non_ascii.py: (TestNonAscii.setUp, TestNonAscii.tearDown): No need to protect BZR_EMAIL anymore. (TestNonAscii._check_OSX_can_roundtrip): The needle. (TestNonAscii.create_base): Add a FIXME describing one root cause.