By THÉRÈSE MARGOLIS The German sportswear brand Puma and Mexico’s Coppel department stores have just signed Grammy-nominee Paty Cantú as their new brand ambassador. As part of the first-ever Coppel Sneaker Fest, Cantú met with fans at the chain’s Oceanía Shopping Mall in Mexico City on Thursday, Aug. 11, to present Puma’s latest sports shoe designs and to talk about