flaky: ignore errors about non existing files in validateFileTree (#8866)

* fix: ignore errors about non existing files in validateFileTree

* Update testing/installtest/checks_unix.go

Co-authored-by: Paolo Chilà <[email protected]>

* Update testing/installtest/checks_unix.go

Co-authored-by: Paolo Chilà <[email protected]>

* fix: add errors import

---------

Co-authored-by: Paolo Chilà <[email protected]>

Author: pkoutsovasilis

testing/installtest/checks_unix.go

@@ -8,6 +8,7 @@ package installtest
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io/fs"
 	"math"
@@ -130,6 +131,9 @@ func checkPlatform(ctx context.Context, _ *atesting.Fixture, topPath string, opt
 func validateFileTree(dir string, uid uint32, gid uint32) error {
 	return filepath.WalkDir(dir, func(file string, d fs.DirEntry, err error) error {
 		if err != nil {
+			if errors.Is(err, fs.ErrNotExist) {
+				return nil
+			}
 			return fmt.Errorf("error traversing the file tree: %w", err)
 		}
 		if d.Type() == os.ModeSymlink {
@@ -138,6 +142,9 @@ func validateFileTree(dir string, uid uint32, gid uint32) error {
 		}
 		info, err := d.Info()
 		if err != nil {
+			if errors.Is(err, fs.ErrNotExist) {
+				return nil
+			}
 			return fmt.Errorf("error caling info: %w", err)
 		}
 		fs, ok := info.Sys().(*syscall.Stat_t)