Jim Fulton writes:

I have attached a new cPickle that adds a new control attribute
to unpicklers:

  Added new Unpickler attribute, find_global.  If set to None, then
  global and instance pickles are disabled.  Otherwise, it should be set to
  a callable object that takes two arguments, a module name and an
  object name, and returns an object.  If the attribute is unset, then
  the default mechanism is used.

  This feature provides an additional mechanism for controlling which
  classes can be used for unpickling.