Revert "Vendor Update"

This reverts commit c2f07f2e95.

vendor/github.com/docker/distribution/registry/api/errcode/handler.go

@@ -1,40 +0,0 @@
-package errcode
-
-import (
-	"encoding/json"
-	"net/http"
-)
-
-// ServeJSON attempts to serve the errcode in a JSON envelope. It marshals err
-// and sets the content-type header to 'application/json'. It will handle
-// ErrorCoder and Errors, and if necessary will create an envelope.
-func ServeJSON(w http.ResponseWriter, err error) error {
-	w.Header().Set("Content-Type", "application/json; charset=utf-8")
-	var sc int
-
-	switch errs := err.(type) {
-	case Errors:
-		if len(errs) < 1 {
-			break
-		}
-
-		if err, ok := errs[0].(ErrorCoder); ok {
-			sc = err.ErrorCode().Descriptor().HTTPStatusCode
-		}
-	case ErrorCoder:
-		sc = errs.ErrorCode().Descriptor().HTTPStatusCode
-		err = Errors{err} // create an envelope.
-	default:
-		// We just have an unhandled error type, so just place in an envelope
-		// and move along.
-		err = Errors{err}
-	}
-
-	if sc == 0 {
-		sc = http.StatusInternalServerError
-	}
-
-	w.WriteHeader(sc)
-
-	return json.NewEncoder(w).Encode(err)
-}