Add Support for options that contains `set` instances

This patch give ability for Options instances to support set objects
as values.
It define __eq__ to avoid calling the fallback method defined in UserDict upper class
ie: UserDict.__cmp__
(cherry picked from commit 4ca599db4e4dfe7f830747dce89d066a0d5d468f)
Signed-off-by: Cédric de Saint Martin <cedric.dsm@tiolive.com>

src/zc/buildout/buildout.py

@@ -1427,6 +1427,20 @@ class Options(UserDict.DictMixin):
         """
         return _convert_bool(name, self[name])
 
+    def __eq__(self, other):
+        """Because __cmp__ calls cmp(self, other)
+        and if self contains set instance, it fails.
+        """
+        if isinstance(other, (UserDict.DictMixin, dict)):
+            for item_self, item_other in itertools.izip_longest(
+                                                            self.iteritems(),
+                                                            other.iteritems()):
+                if item_self != item_other:
+                    return False
+            return True
+        else:
+            return super(Options, self).__eq__(other)
+
 
 def _convert_bool(name, value):
     if value not in ('true', 'false'):