Dear Maintainer,

It seems that xsltproc's xinclude implementation doesn't support https.
This seems to be a known issue upstream, with a patch submitted back
in 2007 - https://mail.gnome.org/archives/xml/2007-March/msg00087.html .
For whatever reason this has never been fixed.

In my case, an xincluded http resource stopped working.  The root
cause was that the http server had been reconfigured to redirect all
http requests to https (this is now quite common, thanks to widespread
use of free SSL certs from letsencrypt).  The error from xsltproc was
not helpful:

error : Unknown IO error
warning: failed to load external entity "http://path/omitted"
input.xml:173: element include: XInclude error : could not load http://path/omitted, and no fallback was found

I only worked out what was going on after stracing xsltproc and seeing
that it got a 301 response from the server, and then looked for a local
file named https://path/omitted .

Ideally, upstream xsltproc's xinclude would support https resources.
An alternative would be for Debian to patch it to do so, since code
to do so does seem to be available.  Failing that, it should be
improved to recognise that an attempt is being made to use an unsupported
URL scheme and explicitly report that in the error message.

(Also, is there a security issue with redirecting from an http URL
to a local file?)


Regards, Phil.