[kubeadm] Update test-case, fix nil-pointer bug, and improve error message

cmd/kubeadm/app/constants/constants.go

@@ -313,7 +313,7 @@ func EtcdSupportedVersion(versionString string) (*version.Version, error) {
 		}
 		return etcdVersion, nil
 	}
-	return nil, fmt.Errorf("Unsupported or unknown kubernetes version")
+	return nil, fmt.Errorf("Unsupported or unknown kubernetes version(%v)", kubernetesVersion)
 }
 
 // GetStaticPodDirectory returns the location on the disk where the Static Pod should be present

cmd/kubeadm/app/constants/constants_test.go

@@ -124,7 +124,7 @@ func TestEtcdSupportedVersion(t *testing.T) {
 		{
 			kubernetesVersion: "1.99.0",
 			expectedVersion:   nil,
-			expectedError:     fmt.Errorf("Unsupported or unknown kubernetes version"),
+			expectedError:     fmt.Errorf("Unsupported or unknown kubernetes version(1.99.0)"),
 		},
 		{
 			kubernetesVersion: "1.9.0",

cmd/kubeadm/app/phases/upgrade/staticpods.go

@@ -222,11 +222,11 @@ func performEtcdStaticPodUpgrade(waiter apiclient.Waiter, pathMgr StaticPodPathM
 	// Need to check currently used version and version from constants, if differs then upgrade
 	desiredEtcdVersion, err := constants.EtcdSupportedVersion(cfg.KubernetesVersion)
 	if err != nil {
-		return true, fmt.Errorf("failed to parse the desired etcd version(%s): %v", desiredEtcdVersion.String(), err)
+		return true, fmt.Errorf("failed to retrieve an etcd version for the target kubernetes version: %v", err)
 	}
 	currentEtcdVersion, err := version.ParseSemantic(etcdStatus.Version)
 	if err != nil {
-		return true, fmt.Errorf("failed to parse the current etcd version(%s): %v", currentEtcdVersion.String(), err)
+		return true, fmt.Errorf("failed to parse the current etcd version(%s): %v", etcdStatus.Version, err)
 	}
 
 	// Comparing current etcd version with desired to catch the same version or downgrade condition and fail on them.

cmd/kubeadm/app/phases/upgrade/staticpods_test.go

@@ -368,7 +368,7 @@ func TestStaticPodControlPlane(t *testing.T) {
 		}
 		defer os.RemoveAll(tmpEtcdDataDir)
 
-		oldcfg, err := getConfig("v1.7.0", tempCertsDir)
+		oldcfg, err := getConfig("v1.9.0", tempCertsDir, tmpEtcdDataDir)
 		if err != nil {
 			t.Fatalf("couldn't create config: %v", err)
 		}
@@ -410,7 +410,7 @@ func TestStaticPodControlPlane(t *testing.T) {
 			t.Fatalf("couldn't read temp file: %v", err)
 		}
 
-		newcfg, err := getConfig("v1.8.0", tempCertsDir)
+		newcfg, err := getConfig("v1.10.0", tempCertsDir, tmpEtcdDataDir)
 		if err != nil {
 			t.Fatalf("couldn't create config: %v", err)
 		}