Web app configures the exception handling middleware but no /Error endpoint exists

From @danroth27
> The web app configures the exception handling middleware to route requests to /Error:
>
> ```csharp
> if (!app.Environment.IsDevelopment())
> {
> app.UseExceptionHandler("/Error");
> // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
> app.UseHsts();
> }
> ```
>
> But no /Error endpoint is defined in the app.
>