Add errors listing to libpod

Signed-off-by: Matthew Heon <mheon@redhat.com>

libpod/container.go

@@ -1,20 +1,15 @@
 package libpod
 
 import (
-	"fmt"
 	"sync"
 
 	"github.com/containers/storage"
 	"github.com/docker/docker/pkg/stringid"
 	spec "github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/pkg/errors"
 	"github.com/ulule/deepcopier"
 )
 
-var (
-	// ErrNotImplemented indicates that functionality is not yet implemented
-	errNotImplemented = fmt.Errorf("NOT IMPLEMENTED")
-)
-
 // Container is a single OCI container
 type Container struct {
 	id   string
@@ -60,7 +55,7 @@ func (c *Container) Spec() *spec.Spec {
 // Make a new container
 func newContainer(rspec *spec.Spec) (*Container, error) {
 	if rspec == nil {
-		return nil, fmt.Errorf("must provide a valid spec to construct container")
+		return nil, errors.Wrapf(ErrInvalidArg, "must provide a valid runtime spec to create container")
 	}
 
 	ctr := new(Container)
@@ -75,52 +70,52 @@ func newContainer(rspec *spec.Spec) (*Container, error) {
 
 // Create creates a container in the OCI runtime
 func (c *Container) Create() error {
-	return errNotImplemented
+	return ErrNotImplemented
 }
 
 // Start starts a container
 func (c *Container) Start() error {
-	return errNotImplemented
+	return ErrNotImplemented
 }
 
 // Stop stops a container
 func (c *Container) Stop() error {
-	return errNotImplemented
+	return ErrNotImplemented
 }
 
 // Kill sends a signal to a container
 func (c *Container) Kill(signal uint) error {
-	return errNotImplemented
+	return ErrNotImplemented
 }
 
 // Exec starts a new process inside the container
 // Returns fully qualified URL of streaming server for executed process
 func (c *Container) Exec(cmd []string, tty bool, stdin bool) (string, error) {
-	return "", errNotImplemented
+	return "", ErrNotImplemented
 }
 
 // Attach attaches to a container
 // Returns fully qualified URL of streaming server for the container
 func (c *Container) Attach(stdin, tty bool) (string, error) {
-	return "", errNotImplemented
+	return "", ErrNotImplemented
 }
 
 // Mount mounts a container's filesystem on the host
 // The path where the container has been mounted is returned
 func (c *Container) Mount() (string, error) {
-	return "", errNotImplemented
+	return "", ErrNotImplemented
 }
 
 // Status gets a container's status
 // TODO this should return relevant information about container state
 func (c *Container) Status() error {
-	return errNotImplemented
+	return ErrNotImplemented
 }
 
 // Export exports a container's root filesystem as a tar archive
 // The archive will be saved as a file at the given path
 func (c *Container) Export(path string) error {
-	return errNotImplemented
+	return ErrNotImplemented
 }
 
 // Commit commits the changes between a container and its image, creating a new
@@ -130,5 +125,5 @@ func (c *Container) Export(path string) error {
 // a new base image will be created from the contents of the container's
 // filesystem
 func (c *Container) Commit() (*storage.Image, error) {
-	return nil, errNotImplemented
+	return nil, ErrNotImplemented
 }