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);
     }
='/guix/diff/doc/fdl-1.3.texi?id=a7283c1d143f843266a0af3f564a86c0cef1ba7b'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/doc/fdl-1.3.texi'>
<input type='hidden' name='id' value='a7283c1d143f843266a0af3f564a86c0cef1ba7b'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=a7283c1d143f843266a0af3f564a86c0cef1ba7b'>root</a>/<a href='/guix/log/doc?id=a7283c1d143f843266a0af3f564a86c0cef1ba7b'>doc</a>/<a href='/guix/log/doc/fdl-1.3.texi?id=a7283c1d143f843266a0af3f564a86c0cef1ba7b'>fdl-1.3.texi</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/doc/fdl-1.3.texi?id=a7283c1d143f843266a0af3f564a86c0cef1ba7b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-03-10 20:26:52 +0100'>2020-03-10</span></td><td><a href='/guix/commit/doc/fdl-1.3.texi?id=21656ffa3b6d78a610f0befced20cc9b4b3baab6'>doc: Use HTTPS for external links.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/contributing.texi
  (14.1 Building from Git,
   14.3 The Perfect Setup,
   14.4.1 Software Freedom,
   14.4.4 Synopses and Descriptions,
   14.5.4 Formatting Code):
   Use HTTPS for @uref{}s and @url{}s that support it.

* doc/fdl-1.3.texi
  (Appendix A GNU Free Documentation License):
  Use HTTPS for @uref{}s and @url{}s that support it.

* doc/guix.texi
  (6.3 Build Systems,
   8.8.4 Networking Services,
   8.8.8 Sound Services,
   8.8.16 Web Services,
   8.11 Name Service Switch,
   12.2 Preparing to Use the Bootstrap Binaries);
   Use HTTPS for @uref{}s and @url{}s that support it.

Signed-off-by: Marius Bakke &lt;mbakke@fastmail.com&gt;
</span></span></td><td>Vitaliy Shatrov</td></tr>