Start trying to improve exceptions and backtraces

When using knots utilities.

knots/web-server.scm

@@ -35,6 +35,7 @@
   #:use-module (web http)
   #:use-module (web request)
   #:use-module (web response)
+  #:use-module (knots)
   #:use-module (knots timeout)
   #:use-module (knots non-blocking)
   #:export (run-knots-web-server
@@ -203,8 +204,7 @@ on the procedure being called at any particular time."
   #f)
 
 (define (default-exception-handler exn request)
-  (let* ((stack (make-stack #t))
-         (error-string
+  (let* ((error-string
           (call-with-output-string
             (lambda (port)
               (simple-format
@@ -212,12 +212,9 @@ on the procedure being called at any particular time."
                "exception when processing: ~A ~A\n"
                (request-method request)
                (uri-path (request-uri request)))
-              (display-backtrace stack port 4)
-              (print-exception
-               port
-               (stack-ref stack 4)
-               '%exception
-               (list exn))))))
+              (print-backtrace-and-exception/knots
+               exn
+               #:port port)))))
     (display error-string
              (current-error-port)))