Keith Richards was facing seven years in prison in 1977 for a massive drug bust at his Toronto hotel room. The night before he was sentenced, he headed to Toronto's Interchange Studios and recorded several songs he'd learned from his late friend Gram Parsons. The highlight was "Sing Me Back Home," a ballad Merle Haggard wrote about his time at San Quentin. For our upcoming issue, Richards spoke with Rolling Stone about his appreciation for Haggard, who died earlier this month, who he calls "one of the great country singers of all time and a hell of a guitar player."I...