Sync typeshed (#1849)

* SplitNamespace should derive from Namespace.

* Add band-aid type-ignore to make tests pass. See #1846.

* Sync typeshed.

Author: gvanrossum

mypy/main.py

@@ -85,7 +85,7 @@ def type_check_only(sources: List[BuildSource],
 MYPYPATH     additional module search path"""
 
 
-class SplitNamespace:
+class SplitNamespace(argparse.Namespace):
     def __init__(self, standard_namespace: object, alt_namespace: object, alt_prefix: str) -> None:
         self.__dict__['_standard_namespace'] = standard_namespace
         self.__dict__['_alt_namespace'] = alt_namespace

test-data/stdlib-samples/3.2/test/test_random.py

@@ -46,7 +46,7 @@ def test_seedargs(self) -> None:
         for arg in [list(range(3)), {'one': 1}]:
             self.assertRaises(TypeError, self.gen.seed, arg)
         self.assertRaises(TypeError, self.gen.seed, 1, 2, 3, 4)
-        self.assertRaises(TypeError, type(self.gen), [])
+        self.assertRaises(TypeError, type(self.gen), [])  # type: ignore  # mypy issue 1846
 
     def test_choice(self) -> None:
         choice = self.gen.choice