errors: use errdefs errors in client and commands

This change moves from specific, global errors to the errdefs errors.
This makes it easy to handle certain classes of errors while still
adding context to the failure.

Signed-off-by: Stephen Day <stephen.day@getcruise.com>

client.go

@@ -137,7 +137,7 @@ func New(address string, opts ...ClientOpt) (*Client, error) {
 		c.conn, c.connector = conn, connector
 	}
 	if copts.services == nil && c.conn == nil {
-		return nil, ErrNoGRPCAndService
+		return nil, errors.Wrap(errdefs.ErrUnavailable, "no grpc connection or services is available")
 	}
 
 	// check namespace labels for default runtime
@@ -196,7 +196,7 @@ type Client struct {
 // Reconnect re-establishes the GRPC connection to the containerd daemon
 func (c *Client) Reconnect() error {
 	if c.connector == nil {
-		return ErrReconnectFailed
+		return errors.Wrap(errdefs.ErrUnavailable, "unable to reconnect to containerd, no connector available")
 	}
 	c.connMu.Lock()
 	defer c.connMu.Unlock()
@@ -219,7 +219,7 @@ func (c *Client) IsServing(ctx context.Context) (bool, error) {
 	c.connMu.Lock()
 	if c.conn == nil {
 		c.connMu.Unlock()
-		return false, ErrNoGRPC
+		return false, errors.Wrap(errdefs.ErrUnavailable, "no grpc connection available")
 	}
 	c.connMu.Unlock()
 	r, err := c.HealthService().Check(ctx, &grpc_health_v1.HealthCheckRequest{}, grpc.WaitForReady(true))
@@ -350,7 +350,7 @@ func (c *Client) Fetch(ctx context.Context, ref string, opts ...RemoteOpt) (imag
 	}
 
 	if fetchCtx.Unpack {
-		return images.Image{}, ErrUnpackNotSupported
+		return images.Image{}, errors.Wrap(errdefs.ErrNotImplemented, "unpack on fetch not supported, try pull")
 	}
 
 	if fetchCtx.PlatformMatcher == nil {
@@ -656,7 +656,7 @@ func (c *Client) Version(ctx context.Context) (Version, error) {
 	c.connMu.Lock()
 	if c.conn == nil {
 		c.connMu.Unlock()
-		return Version{}, ErrNoGRPC
+		return Version{}, errors.Wrap(errdefs.ErrUnavailable, "no grpc connection available")
 	}
 	c.connMu.Unlock()
 	response, err := c.VersionService().Version(ctx, &ptypes.Empty{})