Utils: fix recursion error on pickling

Author: leogama

dill/utils.py

@@ -40,7 +40,7 @@ def discard(self, item):
         except ValueError:
             pass
     def __reduce__(self):
-        return CheckerSet, (self.checker, iter(self))
+        return CheckerSet, (self.checker, tuple(self))
 
 class TransSet(set):
     """transformer set that uses a constructor to modify added items"""
@@ -54,5 +54,5 @@ def discard(self, item):
     def remove(self, item):
         super().remove(self.constructor(item))
     def __reduce__(self):
-        return TransSet, (self.constructor, iter(self))
+        return TransSet, (self.constructor, tuple(self))