message: Allow using more than one converter in the testing harness.
diff: @@ -128,7 +128,13 @@ class TestCase(test.TestCase):
  @contextlib.contextmanager
  def converted(self, entity, converter_module, namespace, *tf_symbols):
  node, ctx = self.prepare(entity, namespace)
  - node = converter_module.transform(node, ctx)
  +
  + if not isinstance(converter_module, (list, tuple)):
  + converter_module = (converter_module,)
  + for m in converter_module:
  + node = m.transform(node, ctx)
  + node = converter.standard_analysis(node, ctx, is_initial=True)
  +
  with self.compiled(node, namespace, *tf_symbols) as result:
  yield result
  