If a post-revprop-change script fails and outputs an error message that includes
XML mark-up characters such as '&' and '<', and sends it to the client over DAV
(RA-neon or RA-serf), the client does not see that message but instead sees an
error message about invalid XML.
The server should escape the special characters before embedding the text into
an XML document, but it does not.
Reported by David Trombley in
<http://svn.haxx.se/users/archive-2007-05/0016.shtml> (version 1.4.3 (r23084),
ra_dav /w neon 0.25.5), and by Jon Foster in
<http://svn.haxx.se/dev/archive-2009-12/0300.shtml> (version 1.6.6, ra_dav).