A documentary following the trial of Russian protest punk band Pussy Riot has premiered at the Sundance Film Festival. Maria Alyokhina, 24 and Nadezhda Tolokonnikova, 22, were convicted of "hooliganism motivated by religious hatred" over the obscenity-laced "punk prayer" against President Vladimir Putin, which they performed at the Christ the Saviour Cathedral on 21 February 2012. They were giv…