Allow sets again.

This is for backwards compatibility with existing code which might use sets.

src/RestrictedPython/Utilities.py

@@ -35,6 +35,12 @@
 utility_builtins['set'] = set
 utility_builtins['frozenset'] = frozenset
 
+try:
+    import sets
+    utility_builtins['sets'] = sets
+except ImportError:
+    pass
+
 try:
     import DateTime
     utility_builtins['DateTime'] = DateTime.DateTime

tests/builtins/test_utilities.py

@@ -1,3 +1,6 @@
+from RestrictedPython._compat import IS_PY3
+import pytest
+
 
 def test_string_in_utility_builtins():
     import string
@@ -28,6 +31,14 @@ def test_set_in_utility_builtins():
     assert utility_builtins['set'] is set
 
 
+@pytest.mark.skipif(IS_PY3,
+                    reason='Python 3 has no longer includes the sets module.')
+def test_sets_in_utility_builtins():
+    from RestrictedPython.Utilities import utility_builtins
+    import sets
+    assert utility_builtins['sets'] is sets
+
+
 def test_frozenset_in_utility_builtins():
     from RestrictedPython.Utilities import utility_builtins
     assert utility_builtins['frozenset'] is frozenset