Add type name info for upb python parse error message in MergeFromStrig(). To  keep same with cpp extension.

PiperOrigin-RevId: 643138099

python/message.c

diff --git a/python/message.c b/python/message.c
index 8e418f0..719f858 100644
--- a/python/message.c
+++ b/python/message.c
@@ -1350,7 +1350,9 @@
       upb_Decode(buf, size, self->ptr.msg, layout, extreg, options, arena);
   Py_XDECREF(bytes);
   if (status != kUpb_DecodeStatus_Ok) {
-    PyErr_Format(state->decode_error_class, "Error parsing message");
+    PyErr_Format(state->decode_error_class,
+                 "Error parsing message with type '%s'",
+                 upb_MessageDef_FullName(msgdef));
     return NULL;
   }
   PyUpb_Message_SyncSubobjs(self);