Here is the code to access the stock move from sale order line on Odoo 8:
class xx_sale_order_line(models.Model):
_inherit = 'sale.order.line'
@api.multi
def get_stock_moves(self, stock_picking_type_codes=['outgoing', 'internal'], values=None):
stock_picking_types = self.env['stock.picking.type'].search( [('code','in',stock_picking_type_codes)])
procurement_orders = self.env['procurement.order'].search([('sale_line_id','=',self.id)])
stock_moves = self.env['stock.move'].search([('procurement_id','in',[procurement_order.id for procurement_order in procurement_orders]),
('picking_type_id','in',[stock_picking_type.id for stock_picking_type in stock_picking_types])
])
return stock_moves