Completed the patch for Bug #215126.

* Fixes an incorrect variable in a PyDict_CheckExact.
* Allow general mapping locals arguments for the execfile() function
  and exec statement.
* Add tests.

Lib/test/test_compile.py

@@ -44,6 +44,63 @@ class TestSpecifics(unittest.TestCase):
         except SyntaxError:
             pass
 
+    def test_exec_with_general_mapping_for_locals(self):
+
+        class M:
+            "Test mapping interface versus possible calls from eval()."
+            def __getitem__(self, key):
+                if key == 'a':
+                    return 12
+                raise KeyError
+            def __setitem__(self, key, value):
+                self.results = (key, value)
+            def keys(self):
+                return list('xyz')
+
+        m = M()
+        g = globals()
+        exec 'z = a' in g, m
+        self.assertEqual(m.results, ('z', 12))
+        try:
+            exec 'z = b' in g, m
+        except NameError:
+            pass
+        else:
+            self.fail('Did not detect a KeyError')
+        exec 'z = dir()' in g, m
+        self.assertEqual(m.results, ('z', list('xyz')))
+        exec 'z = globals()' in g, m
+        self.assertEqual(m.results, ('z', g))
+        exec 'z = locals()' in g, m
+        self.assertEqual(m.results, ('z', m))
+        try:
+            exec 'z = b' in m
+        except TypeError:
+            pass
+        else:
+            self.fail('Did not validate globals as a real dict')
+
+        class A:
+            "Non-mapping"
+            pass
+        m = A()
+        try:
+            exec 'z = a' in g, m
+        except TypeError:
+            pass
+        else:
+            self.fail('Did not validate locals as a mapping')
+
+        # Verify that dict subclasses work as well
+        class D(dict):
+            def __getitem__(self, key):
+                if key == 'a':
+                    return 12
+                return dict.__getitem__(self, key)
+        d = D()
+        exec 'z = a' in g, d
+        self.assertEqual(d['z'], 12)
+
     def test_complex_args(self):
 
         def comp_args((a, b)):