title: Laravel 5.3 withValidator() was executed before validation ends
body: <pre><code>/**
   * Get the validation rules that apply to the request.
   *
   * @return array
   */
  public function rules()
  {
      return [
          'some_id' =&gt; ['required', 'exists:some_model,id'],
      ];
  }
  
  /**
   * Configure the validator instance.
   *
   * @param \Illuminate\Validation\Validator $validator
   * @return void
   */
  public function withValidator(Validator $validator)
  {
      $validator-&gt;after(function (Validator $validator) {
          if ($this-&gt;has('some_id') &amp;&amp; Model::find($this-&gt;get('some_id'))-&gt;eloquent-&gt;isBlocked()) {
              throw CustomException();
          }
      });
  }
  </code></pre>
  
  <ul>
  <li>In Laravel docs it is written that withValidator() works after validation is completed. In my case I have a validation rule 'exists' but withValidator() is executed before that so 'exists' rule was ignored here and error is occurring. </li>
  <li><em>Any suggestion to fix the issue would be really really helpful. Thanks</em></li>
  </ul>