Fix kubectl version should print version info

Kubernetes-commit: 948f4de2dbba3affca2de460d836158cbde5db78

tools/clientcmd/validation.go

@@ -30,11 +30,24 @@ import (
 
 var (
 	ErrNoContext   = errors.New("no context chosen")
-	ErrEmptyConfig = errors.New("no configuration has been provided, try setting KUBERNETES_MASTER environment variable")
+	ErrEmptyConfig = NewEmptyConfigError("no configuration has been provided, try setting KUBERNETES_MASTER environment variable")
 	// message is for consistency with old behavior
 	ErrEmptyCluster = errors.New("cluster has no server defined")
 )
 
+// NewEmptyConfigError returns an error wrapping the given message which IsEmptyConfig() will recognize as an empty config error
+func NewEmptyConfigError(message string) error {
+	return &errEmptyConfig{message}
+}
+
+type errEmptyConfig struct {
+	message string
+}
+
+func (e *errEmptyConfig) Error() string {
+	return e.message
+}
+
 type errContextNotFound struct {
 	ContextName string
 }
@@ -60,9 +73,14 @@ func IsContextNotFound(err error) bool {
 func IsEmptyConfig(err error) bool {
 	switch t := err.(type) {
 	case errConfigurationInvalid:
-		return len(t) == 1 && t[0] == ErrEmptyConfig
+		if len(t) != 1 {
+			return false
+		}
+		_, ok := t[0].(*errEmptyConfig)
+		return ok
 	}
-	return err == ErrEmptyConfig
+	_, ok := err.(*errEmptyConfig)
+	return ok
 }
 
 // errConfigurationInvalid is a set of errors indicating the configuration is invalid.