BUG-1070: log exceptions

When we fail to construct a schema context, we do not log any sensible
cause at all, leaving not nearly enough evidence to pin down the
problem. Step one is to start reporting thrown exceptions.

Change-Id: Ie8ccc8f77eb18dfc385d13b81b5c5094866df177
Signed-off-by: Robert Varga <rovarga@cisco.com>