This patch fixes a crash in the libxml2 bindings for Python 3.x
that 'itstool' stumbles upon when processing UTF-8 data:

  https://issues.guix.gnu.org/issue/37468

Patch by Jan Matejek
from <https://bugzilla.opensuse.org/show_bug.cgi?id=1065270>.

--- libxml2-2.9.5.orig/python/libxml.c
+++ libxml2-2.9.5/python/libxml.c
@@ -1620,6 +1620,7 @@ libxml_xmlErrorFuncHandler(ATTRIBUTE_UNU
     PyObject *message;
     PyObject *result;
     char str[1000];
+    unsigned char *ptr = (unsigned char *)str;
 
 #ifdef DEBUG_ERROR
     printf("libxml_xmlErrorFuncHandler(%p, %s, ...) called\n", ctx, msg);
@@ -1636,12 +1637,20 @@ libxml_xmlErrorFuncHandler(ATTRIBUTE_UNU
 	    str[999] = 0;
         va_end(ap);
 
+#if PY_MAJOR_VERSION >= 3
+        /* Ensure the error string doesn't start at UTF8 continuation. */
+        while (*ptr && (*ptr & 0xc0) == 0x80)
+            ptr++;
+#endif
+
         list = PyTuple_New(2);
         PyTuple_SetItem(list, 0, libxml_xmlPythonErrorFuncCtxt);
         Py_XINCREF(libxml_xmlPythonErrorFuncCtxt);
-        message = libxml_charPtrConstWrap(str);
+        message = libxml_charPtrConstWrap(ptr);
         PyTuple_SetItem(list, 1, message);
         result = PyEval_CallObject(libxml_xmlPythonErrorFuncHandler, list);
+        /* Forget any errors caused in the error handler. */
+        PyErr_Clear();
         Py_XDECREF(list);
         Py_XDECREF(result);
     }
 href='/guix/diff/po/packages/sr.po?id=ce1746819b76fa65d058467c81bd52287a1165f2'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/po/packages/sr.po'>
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<option value='range'>range</option>
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<div class='path'>path: <a href='/guix/log/?id=ce1746819b76fa65d058467c81bd52287a1165f2'>root</a>/<a href='/guix/log/po?id=ce1746819b76fa65d058467c81bd52287a1165f2'>po</a>/<a href='/guix/log/po/packages?id=ce1746819b76fa65d058467c81bd52287a1165f2'>packages</a>/<a href='/guix/log/po/packages/sr.po?id=ce1746819b76fa65d058467c81bd52287a1165f2'>sr.po</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/po/packages/sr.po?id=ce1746819b76fa65d058467c81bd52287a1165f2&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-05-01 18:07:34 +0200'>2022-05-01</span></td><td><a href='/guix/commit/po/packages/sr.po?id=6b4124cdcc203d47dc40158062afa1497d73d592'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>po/guix/ja.po: New file.
po/guix/LINGUAS: Add it.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2022-04-02 18:42:36 +0200'>2022-04-02</span></td><td><a href='/guix/commit/po/packages/sr.po?id=8a208df17fe81fbf34f5a86cc52bb0b8e33c7b96'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/packages/fi.po: New file.
* po/packages/LINGUAS: Add it.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2022-03-01 22:17:18 +0100'>2022-03-01</span></td><td><a href='/guix/commit/po/packages/sr.po?id=8c92d85e06e65c5cdb5f6c75faf8aa33e5a68513'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/doc/guix-cookbook.uk.po: New file.
* po/doc/local.mk: Add uk cookbook.
* doc/local.mk: Add uk cookbook.
* po/guix/fa.po: New file.
* po/guix/uk.po: New file.
* po/guix/LINGUAS: Add fa and uk.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2022-02-04 18:29:00 +0100'>2022-02-04</span></td><td><a href='/guix/commit/po/packages/sr.po?id=8391a99d089322a39cbacb1e6dc2979d8b2ef7c9'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/doc/guix-cookbook.pt_BR.po: New file.
* po/doc/local.mk: Add it.
* doc/local.mk: Add pt_BR cookbook.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2022-01-09 11:35:59 +0100'>2022-01-09</span></td><td><a href='/guix/commit/po/packages/sr.po?id=934b0cdfee2078bad42429427e12d6ee2ddb7fec'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/doc/guix-cookbook.fi.po: New file.
* po/doc/guix-manual.fi.po: New file.
* po/doc/local.mk: Add them.
* doc/local.mk: Add them.
* po/guix/fi.po: New file.
* po/guix/LINGUAS: Add it.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-12-04 19:40:52 +0100'>2021-12-04</span></td><td><a href='/guix/commit/po/packages/sr.po?id=7fcb20a8fa242ab53b9bc97ef0b0367c6a399bd4'>nls: Update translations.</a></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-11-06 14:06:36 +0100'>2021-11-06</span></td><td><a href='/guix/commit/po/packages/sr.po?id=85430a9ea6f32aaae3e34741e292a01a2de62ee0'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/doc/guix-cookbook.es.po: New file.
* po/doc/local.mk: Add 'es' cookbook.
* doc/local.mk: Add 'es' cookbook.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-10-17 22:10:25 +0200'>2021-10-17</span></td><td><a href='/guix/commit/po/packages/sr.po?id=15c91189cb61c579f4289047c79530cefe75215f'>nls: Update translations.</a></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-09-02 04:06:52 +0200'>2021-09-02</span></td><td><a href='/guix/commit/po/packages/sr.po?id=1ff2092a39dc5c7c7cd9b4a0ba4b59f92e738efc'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/packages/it.po: New file.
* po/packages/LINGUAS: Add `it'.
* po/*/*.po: Update translations.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-08-04 14:49:53 +0200'>2021-08-04</span></td><td><a href='/guix/commit/po/packages/sr.po?id=6c10c96fedf707d7be059aeb79bd5c8e2d2fa210'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/doc/guix-cookbook.ru.po: New file.
* po/doc/guix-cookbook.sk.po: New file.
* po/*/*.po: Update translations.
* doc/local.mk (COOKBOOK_LANGUAGES): Add ru and sk.
(info_TEXINFOS): Add Russian and Slovak cookbooks.
* po/doc/local.mk (DOC_COOKBOOK_PO_FILES): Add Russian and Slovak po
files.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-05-10 22:34:43 -0400'>2021-05-10</span></td><td><a href='/guix/commit/po/packages/sr.po?id=21fcced608c93e1ac836cdd9ab8c5d200c667e75'>nls: Update translations.</a></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-04-18 13:17:56 +0200'>2021-04-18</span></td><td><a href='/guix/commit/po/packages/sr.po?id=de4617105ca50d282bda57b59b5a277ae1dc3eb1'>nls: Update 'sr' translations.</a></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2019-05-01 10:49:52 +0200'>2019-05-01</span></td><td><a href='/guix/commit/po/packages/sr.po?id=20ee8883bcb1d75e8e783de5254e11e7142c1e61'>nls: Update translations for de and fr.</a></td><td>Ludovic Courtès</td></tr>