Don't mask the 'set' builtin.

BTrees/_base.py

@@ -147,20 +147,20 @@ class _BucketBase(_Base):
 
 class _SetIteration(object):
 
-    def __init__(self, set, useValues=False, default=None):
-        if set is None:
-            set = ()
-        self.set = set
+    def __init__(self, to_iterate, useValues=False, default=None):
+        if to_iterate is None:
+            to_iterate = ()
+        self.to_iterate = to_iterate
         if useValues:
             try:
-                itmeth = set.iteritems
+                itmeth = to_iterate.iteritems
             except AttributeError:
-                itmeth = set.__iter__
+                itmeth = to_iterate.__iter__
                 useValues = False
             else:
                 self.value = None
         else:
-            itmeth = set.__iter__
+            itmeth = to_iterate.__iter__
 
         self.useValues = useValues
         self._next = itmeth().next

BTrees/tests/test__base.py

@@ -14,6 +14,13 @@
 import unittest
 
 
+def _assertRaises(self, e_type, checked, *args, **kw):
+    try:
+        checked(*args, **kw)
+    except e_type as e:
+        return e
+    self.fail("Didn't raise: %s" % e_type.__name__)
+
 
 class Test_BucketBase(unittest.TestCase):