It is suggested to use _i18n.py per oslo.i18n document.
http://docs.openstack.org/developer/oslo.i18n/usage.html
neutronclient.i18n is now a wrapper module which emits
the derecation warning. It is because might be used in
implementation of the client extensions in other repositories.
Closes-Bug: #1519493
Change-Id: I44969daeedc9a66dd9ad5bf80617516faf245ecc