Merge ~cjwatson/launchpad:py3-decoratedresultset-len into launchpad:master

[Colin Watson]

Allow DecoratedResultSet.__len__

On Python 3, list() calls len() internally to preallocate the correct amount of space if possible. If __len__ is unimplemented, then it falls back to guessing, but ForbiddenAttribute confuses it and results in failing to create the list. Allowing __len__ through the security proxy, even though it's unimplemented, avoids this.

[Ioana Lasc (ilasc)]

review: Approve

diff --git a/lib/lp/services/database/configure.zcml b/lib/lp/services/database/configure.zcml
index 3795b28..48b6aa0 100644
--- a/lib/lp/services/database/configure.zcml
+++ b/lib/lp/services/database/configure.zcml
@@ -14,7 +14,7 @@
 
     <class class="lp.services.database.decoratedresultset.DecoratedResultSet">
         <allow interface="storm.zope.interfaces.IResultSet" />
-        <allow attributes="__getslice__ get_plain_result_set" />
+        <allow attributes="__getslice__ __len__ get_plain_result_set" />
     </class>
 
 </configure>