Add more exception handling to make-resource-pool

As I'm not sure it's working reliably.

guix-data-service/utils.scm

@@ -98,6 +98,15 @@
 
   (let ((channel (make-channel)))
     (spawn-fiber
+     (lambda ()
+       (while #t
+         (with-exception-handler
+             (lambda (exn)
+               (simple-format
+                (current-error-port)
+                "exception in the ~A pool fiber: ~A\n"
+                name
+                exn))
            (lambda ()
              (let loop ((resources '())
                         (available '())
@@ -186,7 +195,8 @@
                    unknown)
                   (loop resources
                         available
-                  waiters))))))
+                        waiters)))))
+           #:unwind? #t))))
 
     channel))