Catch exn instead of exn:fail in daemon, to prevent accidental daemon exits.

src/daemon.rkt

@@ -8,12 +8,15 @@
 (define (daemonize-thunk name boot-thunk)
   (lambda ()
     (let reboot ()
-      (with-handlers* ((exn:fail? (lambda (e)
-                                    (log-error "*** DAEMON CRASHED: ~a ***\n~a"
-                                               name
-                                               (exn->string e))
-                                    (sleep 5)
-                                    (reboot))))
+      ;; We would catch exn:fail? here, but exn:pretty in the web
+      ;; server is a subtype of exn, not of exn:fail, and that causes
+      ;; spurious permanent daemon exits.
+      (with-handlers* ((exn? (lambda (e)
+                               (log-error "*** DAEMON CRASHED: ~a ***\n~a"
+                                          name
+                                          (exn->string e))
+                               (sleep 5)
+                               (reboot))))
         (define result (boot-thunk))
         (log-warning "Daemon thread ~a exited normally (returning ~v)" name result)))))