Update mattermost library (#2152)

* Update mattermost library

* Fix linting

vendor/github.com/mitchellh/go-testing-interface/testing.go

@@ -0,0 +1,112 @@
+package testing
+
+import (
+	"fmt"
+	"log"
+)
+
+// T is the interface that mimics the standard library *testing.T.
+//
+// In unit tests you can just pass a *testing.T struct. At runtime, outside
+// of tests, you can pass in a RuntimeT struct from this package.
+type T interface {
+	Cleanup(func())
+	Error(args ...interface{})
+	Errorf(format string, args ...interface{})
+	Fail()
+	FailNow()
+	Failed() bool
+	Fatal(args ...interface{})
+	Fatalf(format string, args ...interface{})
+	Helper()
+	Log(args ...interface{})
+	Logf(format string, args ...interface{})
+	Name() string
+	Parallel()
+	Skip(args ...interface{})
+	SkipNow()
+	Skipf(format string, args ...interface{})
+	Skipped() bool
+}
+
+// RuntimeT implements T and can be instantiated and run at runtime to
+// mimic *testing.T behavior. Unlike *testing.T, this will simply panic
+// for calls to Fatal. For calls to Error, you'll have to check the errors
+// list to determine whether to exit yourself.
+//
+// Cleanup does NOT work, so if you're using a helper that uses Cleanup,
+// there may be dangling resources.
+//
+// Parallel does not do anything.
+type RuntimeT struct {
+	skipped bool
+	failed  bool
+}
+
+func (t *RuntimeT) Error(args ...interface{}) {
+	log.Println(fmt.Sprintln(args...))
+	t.Fail()
+}
+
+func (t *RuntimeT) Errorf(format string, args ...interface{}) {
+	log.Printf(format, args...)
+	t.Fail()
+}
+
+func (t *RuntimeT) Fail() {
+	t.failed = true
+}
+
+func (t *RuntimeT) FailNow() {
+	panic("testing.T failed, see logs for output (if any)")
+}
+
+func (t *RuntimeT) Failed() bool {
+	return t.failed
+}
+
+func (t *RuntimeT) Fatal(args ...interface{}) {
+	log.Print(args...)
+	t.FailNow()
+}
+
+func (t *RuntimeT) Fatalf(format string, args ...interface{}) {
+	log.Printf(format, args...)
+	t.FailNow()
+}
+
+func (t *RuntimeT) Log(args ...interface{}) {
+	log.Println(fmt.Sprintln(args...))
+}
+
+func (t *RuntimeT) Logf(format string, args ...interface{}) {
+	log.Println(fmt.Sprintf(format, args...))
+}
+
+func (t *RuntimeT) Name() string {
+	return ""
+}
+
+func (t *RuntimeT) Parallel() {}
+
+func (t *RuntimeT) Skip(args ...interface{}) {
+	log.Print(args...)
+	t.SkipNow()
+}
+
+func (t *RuntimeT) SkipNow() {
+	t.skipped = true
+}
+
+func (t *RuntimeT) Skipf(format string, args ...interface{}) {
+	log.Printf(format, args...)
+	t.SkipNow()
+}
+
+func (t *RuntimeT) Skipped() bool {
+	return t.skipped
+}
+
+func (t *RuntimeT) Helper() {}
+
+func (t *RuntimeT) Cleanup(func()) {}