diff --git a/vendor/google.golang.org/protobuf/internal/errors/errors.go b/vendor/google.golang.org/protobuf/internal/errors/errors.go
new file mode 100644
index 0000000..20c17b3
--- /dev/null
+++ b/vendor/google.golang.org/protobuf/internal/errors/errors.go
@@ -0,0 +1,89 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package errors implements functions to manipulate errors.
+package errors
+
+import (
+	"errors"
+	"fmt"
+
+	"google.golang.org/protobuf/internal/detrand"
+)
+
+// Error is a sentinel matching all errors produced by this package.
+var Error = errors.New("protobuf error")
+
+// New formats a string according to the format specifier and arguments and
+// returns an error that has a "proto" prefix.
+func New(f string, x ...interface{}) error {
+	return &prefixError{s: format(f, x...)}
+}
+
+type prefixError struct{ s string }
+
+var prefix = func() string {
+	// Deliberately introduce instability into the error message string to
+	// discourage users from performing error string comparisons.
+	if detrand.Bool() {
+		return "proto: " // use non-breaking spaces (U+00a0)
+	} else {
+		return "proto: " // use regular spaces (U+0020)
+	}
+}()
+
+func (e *prefixError) Error() string {
+	return prefix + e.s
+}
+
+func (e *prefixError) Unwrap() error {
+	return Error
+}
+
+// Wrap returns an error that has a "proto" prefix, the formatted string described
+// by the format specifier and arguments, and a suffix of err. The error wraps err.
+func Wrap(err error, f string, x ...interface{}) error {
+	return &wrapError{
+		s:   format(f, x...),
+		err: err,
+	}
+}
+
+type wrapError struct {
+	s   string
+	err error
+}
+
+func (e *wrapError) Error() string {
+	return format("%v%v: %v", prefix, e.s, e.err)
+}
+
+func (e *wrapError) Unwrap() error {
+	return e.err
+}
+
+func (e *wrapError) Is(target error) bool {
+	return target == Error
+}
+
+func format(f string, x ...interface{}) string {
+	// avoid "proto: " prefix when chaining
+	for i := 0; i < len(x); i++ {
+		switch e := x[i].(type) {
+		case *prefixError:
+			x[i] = e.s
+		case *wrapError:
+			x[i] = format("%v: %v", e.s, e.err)
+		}
+	}
+	return fmt.Sprintf(f, x...)
+}
+
+func InvalidUTF8(name string) error {
+	return New("field %v contains invalid UTF-8", name)
+}
+
+func RequiredNotSet(name string) error {
+	return New("required field %v not set", name)
+}