More Python data model fixes for acme.

acme/jose/jwa.py

@@ -35,7 +35,12 @@ class JWASignature(JWA):
         self.name = name
 
     def __eq__(self, other):
-        return isinstance(other, JWASignature) and self.name == other.name
+        if not isinstance(other, JWASignature):
+            return NotImplemented
+        return self.name == other.name
+
+    def __ne__(self, other):
+        return not self == other
 
     @classmethod
     def register(cls, signature_cls):

acme/jose/jwa_test.py

@@ -44,8 +44,13 @@ class JWASignatureTest(unittest.TestCase):
 
     def test_eq(self):
         self.assertEqual(self.Sig1, self.Sig1)
+
+    def test_ne(self):
         self.assertNotEqual(self.Sig1, self.Sig2)
 
+    def test_ne_other_type(self):
+        self.assertNotEqual(self.Sig1, 5)
+
     def test_repr(self):
         self.assertEqual('Sig1', repr(self.Sig1))
         self.assertEqual('Sig2', repr(self.Sig2))

acme/messages.py

@@ -84,7 +84,7 @@ class _Constant(jose.JSONDeSerializable):
         return isinstance(other, type(self)) and other.name == self.name
 
     def __ne__(self, other):
-        return not self.__eq__(other)
+        return not self == other
 
 
 class Status(_Constant):