[FIX] stock_landed_cost: round former_cost of valuations for total_cost

When computing the total_cost of a landed cost make sure to round the
individual costs of the valuation lines the same way as done by the
ORM (i.e. with the 'Product price' precision).

Otherwise the sum of the additional costs on the valuation lines will
not equal the price of the cost lines. This is wrong and leads to
errors during validation.

opw-804396

addons/stock_landed_costs/stock_landed_costs.py

@@ -288,9 +288,13 @@ def compute_landed_cost(self, cr, uid, ids, context=None):
                     v.update({'cost_id': cost.id, 'cost_line_id': line.id})
                     self.pool.get('stock.valuation.adjustment.lines').create(cr, uid, v, context=context)
                 total_qty += v.get('quantity', 0.0)
-                total_cost += v.get('former_cost', 0.0)
                 total_weight += v.get('weight', 0.0)
                 total_volume += v.get('volume', 0.0)
+
+                former_cost = v.get('former_cost', 0.0)
+                # round this because former_cost on the valuation lines is also rounded
+                total_cost += float_round(former_cost, precision_digits=digits[1]) if digits else former_cost
+
                 total_line += 1
 
             for line in cost.cost_lines: