I just spoke to Tractor Tavern owner Dan Cowan, who says that, as far as he knows, tonight’s Lemonheads show is still on. Why the skepticism? Because last time head Lemon Evan Dando was supposed to play there, he canceled. Only he didn’t really cancel, he just never showed up, finally phoning well after the gig to say he’d overslept (this was late at night, bear in mind).Well apparently Dando’s up to his old tricks, canceling his San Francisco gig two nights ago due to “illness” at the last minute. When we posted something in praise of the Lemonheads’ new cover album last month, a commentator with Tractor ties seemed to have no qualms about giving the handsome Bostonian a shot at redemption. But the San Fran bailout makes one wonder whether he’ll perform proper penance.