Write error to watcher error channel if Start() fails

Up's loop will notice globalCtx is done, and invoke watcher.Stop(). Stop() reads from the watcher error channel. If Start() does not write an error, Stop() will never finish.

Fixes #13262

Author: Trolldemorted

pkg/compose/watch.go

@@ -89,6 +89,9 @@ func (w *Watcher) Start(ctx context.Context) error {
 	w.stopFn = cancelFunc
 	wait, err := w.watchFn(ctx, w.project, w.options)
 	if err != nil {
+		go func() {
+			w.errCh <- err
+		}()
 		return err
 	}
 	go func() {