Add accumulateResources remote file error tests

Test accumulateResources errors when a remote file fails to load. This
is part of the effort to fix issue #4807.

api/testutils/kusttest/ondisk.go

@@ -0,0 +1,29 @@
+// Copyright 2023 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package kusttest_test
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"sigs.k8s.io/kustomize/kyaml/filesys"
+)
+
+// CreateKustDir creates a file system on disk and a new directory
+// that holds a kustomization file with content. The directory is removed on
+// test completion.
+func CreateKustDir(t *testing.T, content string) (filesys.FileSystem, filesys.ConfirmedDir) {
+	t.Helper()
+
+	fSys := filesys.MakeFsOnDisk()
+	tmpDir, err := filesys.NewTmpConfirmedDir()
+	require.NoError(t, err)
+	require.NoError(t, fSys.WriteFile(filepath.Join(tmpDir.String(), "kustomization.yaml"), []byte(content)))
+
+	t.Cleanup(func() {
+		require.NoError(t, fSys.RemoveAll(tmpDir.String()))
+	})
+	return fSys, tmpDir
+}