Former President Donald Trump was the subject of a brutal fact-check Monday after legal experts found his election flier claims that his court cases were keeping from the campaign trail. MSNBC legal expert Lisa Rubin took to the airwaves Monday to explain Trump doesn’t have to appear in court this week for his cases after an email to supporters went viral. “They’re not obligations,” Rubin said. “In fact, in none of these circumstances does former President Trump have to attend at all to the extent that he and his proxies are characterizing these as requirements and obligations.” POLL: Should T…