By THÉRÈSE MARGOLIS     Just days before he is due to step down after a six-year term as president of Mexico, Enrique Peña Nieto raised the price of gasoline on Friday, Nov. 23. Peña Nieto’s Institutional Revolutionary Party (PRI), which ran the country essentially uncontested for more than seven decades until the year 2000, lost overwhelmingly in Mexico’s July 1 elections to