Make the exception message check for malformed UTF-8 source looser so that SyntaxError triggered from UnicodeDecodeError is also acceptable.
diff --git a/Lib/test/test_pep3120.py b/Lib/test/test_pep3120.py
index 85da048..09fedf0 100644
--- a/Lib/test/test_pep3120.py
+++ b/Lib/test/test_pep3120.py
@@ -19,7 +19,8 @@
         try:
             import test.badsyntax_pep3120
         except SyntaxError as msg:
-            self.assertTrue(str(msg).find("Non-UTF-8 code starting with") >= 0)
+            msg = str(msg)
+            self.assertTrue('UTF-8' in msg or 'utf8' in msg)
         else:
             self.fail("expected exception didn't occur")