def run_tenuous(self):
with LiveExecution.lock:<EOL><INDENT>ns_snapshot = copy.copy(self.ns)<EOL>try:<EOL><INDENT>source = self.edited_source<EOL>self.edited_source = None<EOL>self.do_exec(source, ns_snapshot)<EOL>self.known_good = source<EOL>self.call_good_cb()<EOL>return True, None<EOL><DEDENT>except Exception as ex:<EOL><INDENT>tb = traceback.format_exc()<EOL>self.call_bad_cb(tb)<EOL>self.ns.clear()<EOL>self.ns.update(ns_snapshot)<EOL>return False, ex<EOL><DEDENT><DEDENT>
Run edited source, if no exceptions occur then it
graduates to known good.