Unprintable exception PathsNotVersionedError

Trying to commit a non-ascii path that is not versioned such as in bug 714449 has started giving the following error output:

    bzr: ERROR: Unprintable exception PathsNotVersionedError: dict={'paths': ['\xc2\xa3'], '_preformatted_string': None, 'paths_as_string': '"\xc2\xa3"'}, fmt='Path(s) are not versioned: %(paths_as_string)s', error=UnicodeDecodeError('ascii', '"\xc2\xa3"', 1, 2, 'ordinal not in range(128)')

The expected, and previously given output is:

    bzr: ERROR: Path(s) are not versioned: "£"

The regresion bisects to r6123.1.10 (formerly known as r6133) which is the enabling of gettext for errors.