Add a user friendly message about what's happening...

Still in the abnormal termination case. pgloader might get stuck and if the
user knows it's waiting for threads to complete, they might be less worried
about the situation and opportunity to kill pgloader...

src/main.lisp

@@ -354,6 +354,8 @@
                 (declare (ignore c))    ; handler-bind printed it out
                 (format *error-output* "~%What I am doing here?~%~%")
                 ;; wait until monitor stops...
+                (format *error-output*
+                        "~%Waiting for the monitor thread to complete.~%~%")
                 (let ((lp:*kernel* *monitoring-kernel*))
                   (lp:end-kernel :wait t))
                 (uiop:quit +os-code-error+)))))