Index: Python/errors.c
===================================================================
--- Python/errors.c	(revision 62102)
+++ Python/errors.c	(working copy)
@@ -108,7 +108,14 @@
 	if (PyExceptionClass_Check(err) && PyExceptionClass_Check(exc)) {
 		/* problems here!? not sure PyObject_IsSubclass expects to
 		 be called with an exception pending... */
-		return PyObject_IsSubclass(err, exc);
+		int res = PyObject_IsSubclass(err, exc);
+		/* This function must not fail, so print the error here */
+		if (res == -1) {
+			PyErr_WriteUnraisable(err);
+			/* return arbitrary value */
+			res = 0;
+		}
+		return res;
 	}
 
 	return err == exc;
</div><div class="naked_ctrl">
<form action="/index.cgi/contrast" method="get" name="gate">
<p><a href="http://altstyle.alfasado.net">AltStyle</a> によって変換されたページ <a href="https://bugs.python.org/file9931/errors.diff">(-&gt;オリジナル)</a>
/ <label>アドレス: <input type="text" name="naked_post_url" value="https://bugs.python.org/file9931/errors.diff" size="22" /></label> <label>モード: <select name="naked_post_mode">
<option value="default">デフォルト</option>
<option value="speech">音声ブラウザ</option>
<option value="ruby">ルビ付き</option>
<option value="contrast" selected="selected">配色反転</option>
<option value="larger-text">文字拡大</option>
<option value="mobile">モバイル</option>
</select>
<input type="submit" value="表示" />
</p>
</form>
</div>