Users and project owners can configure invalid watch filters. Logging each invalid filter with stacktrace on warning level for each change where the filter may apply is much too noisy in the log. Logging the execption message is enough to know what's wrong with a filter. Signed-off-by: Edwin Kempin <ekempin@google.com> Change-Id: I7bd94adb9fc9608134a3b8e1570212250a694bf6