Convert Python types to proper Python type hierarchy.

Now much more inline with how CPython does types.
diff --git a/py/compile.c b/py/compile.c
index f8fa2cb..0e19890 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -1316,7 +1316,7 @@
 void compile_assert_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
     int l_end = comp_next_label(comp);
     c_if_cond(comp, pns->nodes[0], true, l_end);
-    EMIT(load_id, MP_QSTR_assertion_error);
+    EMIT(load_id, MP_QSTR_AssertionError);
     if (!MP_PARSE_NODE_IS_NULL(pns->nodes[1])) {
         // assertion message
         compile_node(comp, pns->nodes[1]);