exception_view.py

@view_config(context=Exception)
def exception_view(context, request):
    # Check to see if debug toolbar is enabled.
    from pyramid.interfaces import ITweens
    tweens = request.registry.queryUtility(ITweens)
    if tweens:
        tween_list = tweens.explicit or tweens.implicit()
        tween_names = zip(*tween_list)[0]
        if tween_list and 'pyramid_debugtoolbar.toolbar_tween_factory' in\
           tween_names:
            raise  # Re-raise exception for debug toolbar.
    # Exception handler goes here ;)