Initial kubetest2 structure for e2e testing

This creates a new go module for the e2e code and the kubetest2 skeleton.
Most of the kubetest2 code was copied from sigs.k8s.io/kubetest2/kubetest2-gke.

Currently only building (`make gcs-publish-ci`) is in place.
I used test-infra/scenarios/kubernetes_e2e.py as reference, removing env and make variables that are no longer needed.

Instructions:
```
cd tests/e2e
go install sigs.k8s.io/kubetest2
go install ./kubetest2-kops
kubetest2 kops -v 9 --build --stage-location=gs://foobar/ --kops-root=../../  # runs make gcs-publish-ci and exits
```

tests/e2e/go.mod

@@ -0,0 +1,10 @@
+module k8s.io/kops/tests/e2e
+
+go 1.15
+
+require (
+	github.com/octago/sflags v0.2.0
+	github.com/spf13/pflag v1.0.5
+	k8s.io/klog/v2 v2.3.0
+	sigs.k8s.io/kubetest2 v0.0.0-20200930205053-4e57931be178
+)

tests/e2e/kubetest2-kops/builder/build.go

@@ -0,0 +1,42 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package builder
+
+import (
+	"fmt"
+	"os"
+
+	"sigs.k8s.io/kubetest2/pkg/exec"
+)
+
+type BuildOptions struct {
+	KopsRoot      string `flag:"-"`
+	StageLocation string `flag:"-"`
+}
+
+// Build will build the kops artifacts and publish them to the stage location
+func (b *BuildOptions) Build() error {
+	cmd := exec.Command("make", "gcs-publish-ci")
+	cmd.SetEnv(
+		fmt.Sprintf("HOME=%v", os.Getenv("HOME")),
+		fmt.Sprintf("PATH=%v", os.Getenv("PATH")),
+		fmt.Sprintf("GCS_LOCATION=%v", b.StageLocation),
+	)
+	cmd.SetDir(b.KopsRoot)
+	exec.InheritOutput(cmd)
+	return cmd.Run()
+}

tests/e2e/kubetest2-kops/deployer/build.go

@@ -0,0 +1,53 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package deployer
+
+import (
+	"errors"
+	"os"
+	"strings"
+)
+
+func (d *deployer) Build() error {
+	if err := d.init(); err != nil {
+		return err
+	}
+	if err := d.BuildOptions.Build(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (d *deployer) verifyBuildFlags() error {
+	if d.KopsRoot == "" {
+		return errors.New("required kops-root when building from source")
+	}
+	if !strings.HasPrefix(d.StageLocation, "gs://") {
+		return errors.New("stage-location must be a gs:// path")
+	}
+	fi, err := os.Stat(d.KopsRoot)
+	if err != nil {
+		return err
+	}
+	if !fi.Mode().IsDir() {
+		return errors.New("kops-root must be a directory")
+	}
+
+	d.BuildOptions.KopsRoot = d.KopsRoot
+	d.BuildOptions.StageLocation = d.StageLocation
+	return nil
+}

tests/e2e/kubetest2-kops/deployer/common.go

@@ -0,0 +1,35 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package deployer
+
+import "fmt"
+
+func (d *deployer) init() error {
+	var err error
+	d.doInit.Do(func() { err = d.initialize() })
+	return err
+}
+
+// initialize should only be called by init(), behind a sync.Once
+func (d *deployer) initialize() error {
+	if d.commonOptions.ShouldBuild() {
+		if err := d.verifyBuildFlags(); err != nil {
+			return fmt.Errorf("init failed to check build flags: %s", err)
+		}
+	}
+	return nil
+}

tests/e2e/kubetest2-kops/deployer/deployer.go

@@ -0,0 +1,100 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package deployer implements the kubetest2 Kops deployer
+package deployer
+
+import (
+	"flag"
+	"sync"
+
+	"github.com/octago/sflags/gen/gpflag"
+	"github.com/spf13/pflag"
+	"k8s.io/klog/v2"
+	"k8s.io/kops/tests/e2e/kubetest2-kops/builder"
+
+	"sigs.k8s.io/kubetest2/pkg/types"
+)
+
+// Name is the name of the deployer
+const Name = "kops"
+
+type deployer struct {
+	// generic parts
+	commonOptions types.Options
+	// doInit helps to make sure the initialization is performed only once
+	doInit sync.Once
+
+	KopsRoot      string `flag:"kops-root" desc:"Path to root of the kops repo. Used with --build."`
+	StageLocation string `flag:"stage-location" desc:"Storage location for kops artifacts. Only gs:// paths are supported."`
+	BuildOptions  *builder.BuildOptions
+}
+
+// assert that New implements types.NewDeployer
+var _ types.NewDeployer = New
+
+// assert that deployer implements types.Deployer
+var _ types.Deployer = &deployer{}
+
+func (d *deployer) Provider() string {
+	return Name
+}
+
+func (d *deployer) Up() error {
+	klog.Warning("Up is not implemented")
+	return nil
+}
+
+func (d *deployer) IsUp() (bool, error) {
+	klog.Warning("IsUp is not implemented")
+	return true, nil
+}
+
+func (d *deployer) Down() error {
+	klog.Warning("Down is not implemented")
+	return nil
+}
+
+func (d *deployer) DumpClusterLogs() error {
+	klog.Warning("DumpClusterLogs is not implemented")
+	return nil
+}
+
+// New implements deployer.New for kops
+func New(opts types.Options) (types.Deployer, *pflag.FlagSet) {
+	// create a deployer object and set fields that are not flag controlled
+	d := &deployer{
+		commonOptions: opts,
+		BuildOptions:  &builder.BuildOptions{},
+	}
+
+	// register flags
+	fs := bindFlags(d)
+
+	// register flags for klog
+	klog.InitFlags(nil)
+	fs.AddGoFlagSet(flag.CommandLine)
+	return d, fs
+}
+
+func bindFlags(d *deployer) *pflag.FlagSet {
+	flags, err := gpflag.Parse(d)
+	if err != nil {
+		klog.Fatalf("unable to generate flags from deployer")
+		return nil
+	}
+	return flags
+}

tests/e2e/kubetest2-kops/main.go

@@ -0,0 +1,27 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"sigs.k8s.io/kubetest2/pkg/app"
+
+	"k8s.io/kops/tests/e2e/kubetest2-kops/deployer"
+)
+
+func main() {
+	app.Main(deployer.Name, deployer.New)
+}