Fix tests in Py2.

tests/run/addop.pyx

@@ -176,7 +176,10 @@ def add0(x):
     (1, 1)
     >>> add0(-1)
     (-1, -1)
-    >>> add0(2**32)
-    (4294967296, 4294967296)
+    >>> a, b = add0(2**32)
+    >>> bigint(a)
+    4294967296
+    >>> bigint(b)
+    4294967296
     """
     return x + 0, 0 + x

tests/run/subop.pyx

@@ -203,9 +203,15 @@ def sub0(x):
     (-1, 1)
     >>> sub0(99)
     (99, -99)
-    >>> sub0(2**32)
-    (4294967296, -4294967296)
-    >>> sub0(-2**32)
-    (-4294967296, 4294967296)
+    >>> a, b = sub0(2**32)
+    >>> bigint(a)
+    4294967296
+    >>> bigint(b)
+    -4294967296
+    >>> a, b = sub0(-2**32)
+    >>> bigint(a)
+    -4294967296
+    >>> bigint(b)
+    4294967296
     """
     return x - 0, 0 - x