Raise more meaningful exception when trying to access methods on the Courier handler.
Raise more meaningful exception when trying to access methods on the Courier handler.

PiperOrigin-RevId: 427119114
Change-Id: Ic82a8ed5ed9300a72fac1ce58dc9a636ca414aff

deepmind/launchpad,deepmind/launchpad,deepmind/launchpad,deepmind/launchpad