Update to Expat 1.95.7; there are no changes to the Expat sources.
diff --git a/Modules/expat/xmltok_impl.c b/Modules/expat/xmltok_impl.c
index 84a3267..46569fe 100644
--- a/Modules/expat/xmltok_impl.c
+++ b/Modules/expat/xmltok_impl.c
@@ -882,7 +882,7 @@
                     const char **nextTokPtr)
 {
   if (ptr == end)
-    return XML_TOK_PARTIAL;
+    return -XML_TOK_PERCENT;
   switch (BYTE_TYPE(enc, ptr)) {
   CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
   case BT_S: case BT_LF: case BT_CR: case BT_PERCNT: