laravel5.2→5.3 boot関数の引数削除

    public function boot(GateContract $gate)
    {
        $this->registerPolicies($gate);

        //
    }

後

public function boot()
    {
        $this->registerPolicies();

        //
    }

EvenServiceProvider.php
前

public function boot(DispatcherContract $events)
    {
        parent::boot($events);

        //
    }

後

public function boot()
    {
        parent::boot();

        //
    }

RouteServiceProvider.php

public function boot(Router $router)
    {
        //

        parent::boot($router);
    }

public function boot()
    {
        //

        parent::boot();
    }

再度アップデートしてみる。
[vagrant@localhost blog]$ php composer.phar update
Loading composer repositories with package information
Updating dependencies (including require-dev)
Nothing to install or update
Package phpunit/phpunit-mock-objects is abandoned, you should avoid using it. No replacement was suggested.
Generating autoload files
> Illuminate\Foundation\ComposerScripts::postUpdate
> php artisan optimize
Generating optimized class loader
The compiled class file has been removed.

とりあえずエラーは出なくなりましたね。