lib: improve wait.For returns. (#1403)

platform/wait/wait.go

@@ -1,6 +1,7 @@
 package wait
 
 import (
+	"errors"
 	"fmt"
 	"time"
 
@@ -16,6 +17,9 @@ func For(msg string, timeout, interval time.Duration, f func() (bool, error)) er
 	for {
 		select {
 		case <-timeUp:
+			if lastErr == nil {
+				return errors.New("time limit exceeded")
+			}
 			return fmt.Errorf("time limit exceeded: last error: %w", lastErr)
 		default:
 		}

platform/wait/wait_test.go

@@ -13,13 +13,14 @@ func TestForTimeout(t *testing.T) {
 		})
 	}()
 
-	timeout := time.After(5 * time.Second)
+	timeout := time.After(6 * time.Second)
 	select {
 	case <-timeout:
 		t.Fatal("timeout exceeded")
 	case err := <-c:
 		if err == nil {
 			t.Errorf("expected timeout error; got %v", err)
 		}
+		t.Logf("%v", err)
 	}
 }