record: removed 'has_key' usage

Py3k has removed the dictionary has_key method. This patch implements
a one argument function that can be used as a callback by hg.revert in
the record extension.

hgext/record.py

@@ -486,7 +486,8 b' def dorecord(ui, repo, commitfunc, *pats'
 
             # 3a. apply filtered patch to clean repo  (clean)
             if backups:
-                hg.revert(repo, repo.dirstate.parents()[0], backups.has_key)
+                hg.revert(repo, repo.dirstate.parents()[0],
+                          lambda key: key in backups)
 
             # 3b. (apply)
             if dopatch: