Richard Leonard has said the row over whether a leadership challenge can be mounted against the embattled Scottish Labour leader could end up in the courts.MSP Daniel Johnson, who has urged Leonard to stand down, said the view that Holyrood colleagues cannot trigger a contest is legally challengeable.Leonard is fighting to hold on to his job after a mutiny by MSP colleagues.Johnson, James Kelly, Jenny Marra and Mark Griffin have all called on the left-winger to quit, as have four party peers.As