John Hopewell Chief International CorrespondentIn a deal struck on the cusp of San Sebastian Film Festival, Germany’s Pandora Filmproduktion has boarded “Riders,” the latest project from Martín Rejtman, hailed as the founding father of the New Argentine Cinema.Written by Rejtman, “Riders” (“El Repartidor Está en Camino”) will be presented to further potential partners at this weekend’s 9th’s San Sebastian Europe-Latin America Co-Production Forum.Set up at Buenos Aires’ Un Puma, headed by María