Tensions are high along the border between Colombia and Venezuela, as a major push to deliver humanitarian aid could descend into violence on Saturday. On Friday, musicians held a Live Aid Venezuela concert in border town Cucuta, Colombia to pressure Venezuelan leader Nicolas Maduro to let humanitarian aid into Venezuela, ending the show with a rendition of John Lennon's "Imagine." Concert organizer Richard Branson also took the concert stage, exhorting the crowd in a…