Sale of realty by trustee by virtue of pledge or deed of trust

No sale of real estate by a trustee, by virtue of a pledge or deed of trust to secure the payment of debts, shall be valid or pass the title of the property specified in the deed or pledge, unless the sale is in pursuance to a judgment of court, or is made by an assignee under a voluntary deed of assignment, or unless the maker of the deed or pledge joins in a writing evidencing the sale.