Fix missing newline in IncreaseLevel error messages (uber-go#828)

Author: SteelPhase

increase_level_test.go

@@ -58,7 +58,7 @@ func TestIncreaseLevelTryDecrease(t *testing.T) {
 			newLoggedEntry(ErrorLevel, "increase level error log"),
 		}, logs.AllUntimed(), "unexpected logs")
 		assert.Equal(t,
-			`failed to IncreaseLevel: invalid increase level, as level "info" is allowed by increased level, but not by existing core`,
+			"failed to IncreaseLevel: invalid increase level, as level \"info\" is allowed by increased level, but not by existing core\n",
 			errorOut.String(),
 			"unexpected error output",
 		)

options.go

@@ -125,7 +125,7 @@ func IncreaseLevel(lvl zapcore.LevelEnabler) Option {
 	return optionFunc(func(log *Logger) {
 		core, err := zapcore.NewIncreaseLevelCore(log.core, lvl)
 		if err != nil {
-			fmt.Fprintf(log.errorOutput, "failed to IncreaseLevel: %v", err)
+			fmt.Fprintf(log.errorOutput, "failed to IncreaseLevel: %v\n", err)
 		} else {
 			log.core = core
 		}