cli/command/system: remove errdefs uses

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Author: thaJeztah

cli/command/system/prune.go

@@ -18,7 +18,6 @@ import (
 	"github.com/docker/cli/internal/prompt"
 	"github.com/docker/cli/opts"
 	"github.com/docker/docker/api/types/versions"
-	"github.com/docker/docker/errdefs"
 	"github.com/docker/go-units"
 	"github.com/fvbommel/sortorder"
 	"github.com/pkg/errors"
@@ -83,7 +82,7 @@ func runPrune(ctx context.Context, dockerCli command.Cli, options pruneOptions)
 			return err
 		}
 		if !r {
-			return errdefs.Cancelled(errors.New("system prune has been cancelled"))
+			return cancelledErr{errors.New("system prune has been cancelled")}
 		}
 	}
 	pruneFuncs := []func(ctx context.Context, dockerCli command.Cli, all bool, filter opts.FilterOpt) (uint64, string, error){
@@ -115,6 +114,10 @@ func runPrune(ctx context.Context, dockerCli command.Cli, options pruneOptions)
 	return nil
 }
 
+type cancelledErr struct{ error }
+
+func (cancelledErr) Cancelled() {}
+
 // confirmationMessage constructs a confirmation message that depends on the cli options.
 func confirmationMessage(dockerCli command.Cli, options pruneOptions) string {
 	t := template.Must(template.New("confirmation message").Parse(confirmationTemplate))