The ``ext_pillar`` functions **must** now accept a minion ID as the first argument.
This stops the deprecation path started in Salt 0.17.x. Before this minion ID first argument was introduced, the minion ID could be retrieved accessing ``__opts__['id']`` loosing the reference to the master ID initially set in opts.
This is no longer the case, ``__opts__['id']`` will be kept as the master ID.