Another bug fix for recent import * warning (caught by Thomas Wouters)

Only return if symtable_warn() returns -1, indicating that the warning
was turned into an error.

Python/compile.c

@@ -5295,8 +5295,8 @@ symtable_import(struct symtable *st, node *n)
 		}
 		if (TYPE(CHILD(n, 3)) == STAR) {
 			if (st->st_cur->ste_type != TYPE_MODULE) {
-				symtable_warn(st,
-				      "import * only allowed at module level");
+				if (symtable_warn(st,
+				  "import * only allowed at module level") < 0)
 					return;
 			}
 			st->st_cur->ste_optimized |= OPT_IMPORT_STAR;