Elide unstable OverflowError message.

tests/run/cpp_stl_conversion.pyx

@@ -125,7 +125,7 @@ def test_typedef_vector(o):
     >>> test_typedef_vector([1, 2, 3**100])
     Traceback (most recent call last):
     ...
-    OverflowError: Python int too large to convert to C long
+    OverflowError: ...
     >>> test_typedef_vector([1, 2, None])
     Traceback (most recent call last):
     ...