Dynamic modules don't necessarily have a __package__ attribute

cloudpickle/cloudpickle.py

@@ -385,7 +385,7 @@ def _save_subimports(self, code, top_level_dependencies):
         """
         # check if any known dependency is an imported package
         for x in top_level_dependencies:
-            if isinstance(x, types.ModuleType) and x.__package__:
+            if isinstance(x, types.ModuleType) and hasattr(x, '__package__') and x.__package__:
                 # check if the package has any currently loaded sub-imports
                 prefix = x.__name__ + '.'
                 for name, module in sys.modules.items():

tests/cloudpickle_test.py

@@ -680,6 +680,22 @@ def foo():
         finally:
             sys.modules.pop("_fake_module", None)
 
+    def test_dynamic_pytest_module(self):
+        # Test case for pull request https://github.com/cloudpipe/cloudpickle/pull/116
+        import py
+
+        def f():
+            s = py.builtin.set([1])
+            return s.pop()
+
+        # some setup is required to allow pytest apimodules to be correctly serializable.
+        from cloudpickle import CloudPickler
+        from py._apipkg import ApiModule
+        CloudPickler.dispatch[ApiModule] = CloudPickler.save_module
+        g = cloudpickle.loads(cloudpickle.dumps(f))
+
+        result = g()
+        self.assertEqual(1, result)
 
 if __name__ == '__main__':
     unittest.main()