Made new tests ``test_mapping`` conform to the requirements for a ``dict``...

Made new tests ``test_mapping`` conform to the requirements for a ``dict`` initializer in Python 2.3.x.

NEWS.txt

@@ -10,6 +10,9 @@ development) since ZODB 3.4's last public release:
 PersistentMapping
 -----------------
 
+- (3.4.3b1) Made new tests ``test_mapping`` conform to the requirements for
+  a ``dict`` initializer in Python 2.3.x.
+
 - (3.4.3b1) The ``PersistentMapping`` makes changes by a ``pop()`` method call
   persistent now.
 

src/persistent/tests/test_mapping.py

@@ -38,6 +38,8 @@ class TestPMapping(unittest.TestCase):
         class OtherMapping:
             def __init__(self, initmapping):
                 self.__data = initmapping
+            def keys(self):
+                return self.__data.keys()
             def items(self):
                 return self.__data.items()
         v0 = PersistentMapping(OtherMapping(u0))