By Lizzy Buchan The SNP could face another bitter leadership contest as an eleventh-hour challenge looked set to derail John Swinney’s coronation as First Minister. Veteran SNP activist Graeme McCormick, who branded the Scottish Government’s independence strategy “flatulence in a trance” last year, is battling to secure enough nominations to get onto the ballot paper. Mr Swinney had looked like he would become SNP leader and First Minister uncontested after rival Kate Forbes ruled herself out of the race. But SNP rules allow anyone who can get 100 signatures from 20 branches to run to be party…