[pyramid] Fix 404 handling
Avoid seeing a traceback in the UI by catching it before it reaches pyramid and
restore usage of the '404' view.
Closes #16159863
option_group_changed('port', 'main', 'web')
option_group_changed('query-log-file', 'main', 'web')
option_group_changed('profile', 'main', 'web')
option_group_changed('max-post-length', 'main', 'web')