Those classes are used in neutron to implement custom attribute
and sub-attribute checks (get_network:attr:subattr syntax).
Those checks do not belong to oslo.policy since they would be
backwards incompatible with existing behaviour, introducing new
semantics and potentially breaking other projects, like nova.
So the alternative is to expose those symbols as part of public
API for the oslo library and allow other projects to reuse them.
More details on neutron issues consuming the library can be
found at:
http://lists.openstack.org/pipermail/openstack-dev/2015-April/061783.html
Related-Bug: #1426082
Change-Id: I6ee9f8f7fcea3ddb2c52b5d58dfce3dd328c9131
08215c5353