Part of lp.layers View In Hierarchy
PageTestLayerlayer. (need to register a 404 view for this and for the debug page too. and make the debugview a base class in the debug view and make system error, not found and unauthorized and forbidden views.
This layer is applied to the request that is used for running page tests. Pages registered with this layer are accessible to pagetests but return 404s when visited interactively, so this should be used only for pages we want to maintain but not expose to users.
The SystemErrorView base class looks at the request to see if it provides this interface. If so, it renders tracebacks as plain text.