extdiff: prevent exception on double-translation The docstring is translated twice: once when used as a format string, and once on display. The second translation fails when the first translation introduces non-ASCII characters in the string. The problem is that the gettext module calls unicode(message) on the string, i.e., it decodes it to a Unicode string using the ASCII encoding (the default encoding). By translating it into a Unicode string here, the unicode() call becomes a noop.