Update mattermost library (#2152)

* Update mattermost library

* Fix linting

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

@@ -0,0 +1,12 @@
+language: go
+
+go:
+    - 1.x
+    - tip
+
+script:
+    - go test
+
+matrix:
+    allow_failures:
+        - go: tip

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

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2016 Mitchell Hashimoto
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

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

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+# go-testing-interface
+
+go-testing-interface is a Go library that exports an interface that
+`*testing.T` implements as well as a runtime version you can use in its
+place.
+
+The purpose of this library is so that you can export test helpers as a
+public API without depending on the "testing" package, since you can't
+create a `*testing.T` struct manually. This lets you, for example, use the
+public testing APIs to generate mock data at runtime, rather than just at
+test time.
+
+## Usage & Example
+
+For usage and examples see the [Godoc](http://godoc.org/github.com/mitchellh/go-testing-interface).
+
+Given a test helper written using `go-testing-interface` like this:
+
+    import "github.com/mitchellh/go-testing-interface"
+
+    func TestHelper(t testing.T) {
+        t.Fatal("I failed")
+    }
+
+You can call the test helper in a real test easily:
+
+    import "testing"
+
+    func TestThing(t *testing.T) {
+        TestHelper(t)
+    }
+
+You can also call the test helper at runtime if needed:
+
+    import "github.com/mitchellh/go-testing-interface"
+
+    func main() {
+        TestHelper(&testing.RuntimeT{})
+    }
+
+## Versioning
+
+The tagged version matches the version of Go that the interface is
+compatible with. For example, the version "1.14.0" is for Go 1.14 and
+introduced the `Cleanup` function. The patch version (the ".0" in the
+prior example) is used to fix any bugs found in this library and has no
+correlation to the supported Go version.
+
+## Why?!
+
+**Why would I call a test helper that takes a *testing.T at runtime?**
+
+You probably shouldn't. The only use case I've seen (and I've had) for this
+is to implement a "dev mode" for a service where the test helpers are used
+to populate mock data, create a mock DB, perhaps run service dependencies
+in-memory, etc.
+
+Outside of a "dev mode", I've never seen a use case for this and I think
+there shouldn't be one since the point of the `testing.T` interface is that
+you can fail immediately.

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()) {}