BUG-891: do not drop events silently

As it turns out, infrastructure silently drops things on the floor if
exceptions happen. When these exceptions occur, they hint at major
problems. Promote tham to warnings.

Change-Id: Ib4afdc7ff1a17e562211b3cfbb30735a592d0a2d
Signed-off-by: Robert Varga <rovarga@cisco.com>