Fix build error in debug

std::exception doesn't have a direct conversion to iostream.  This only
shows up when building for debug.

Tested:
Forced -DCMAKE_BUILD_TYPE=Debug, and verified code builds.

Signed-off-by: Ed Tanous <ed@tanous.net>
Change-Id: I6fdd0e561f1cecc5f40f0e8b9c624f746ce6456f