Laravel 5.5 - Method [validationRequired] does not exist

I have a very weird problem. When I'm submitting the form, it throws an error with server-side validation.

BadMethodCallException

Method [validationRequired] does not exist.

My controller:

    public function store(Request $request)
{
    $rules = array(
        'DateDebut' => 'required',
        'TimeDebut' => 'required',
    );

    $messages = [
        'DateDebut.required'=>'La date de début de réunion est obligatoire.',
        'TimeDebut.required'=>'L\'heure de début de réunion est obligatoire.'
    ];
    $validator = Validator::make($request->all(),$rules,$messages);

    if ($validator->fails()) {
        return redirect()->route('demandes.create')
            ->withErrors($validator->errors()->messages());
    } else {
        return view('demandes.index');
    }
}

The controller fails on the methode $validator->fails()

via Chebli Mohamed