title: Odoo v10 @onchange(stage_id) doesn't work with <field name="stage_id" widget="statusbar" clickable="True"/>
body: <p>Odoo v10 @onchange(stage_id) doesn't work with stage_id widget field. When I added field simple field in form body it worked, but not with original:</p>
  
  <pre><code>&lt;field name="stage_id" widget="statusbar" clickable="True"/&gt;
  
  class TaskExtension(models.Model):
      _name = 'project.task'
      _inherit = ['project.task']
  
      @api.model('stage_id', 'date_deadline')
      def _onchange_responsible(self):
          self.user_id = self.stage_id.responsible
  
  
      user_id = fields.Many2one('res.users',string = 'Assigned To',computed = _onchange_responsible,store=True)
  </code></pre>