Skip reading stdout from the solver that if it isn't a line reading only "sat", "unsat", or "unknown".

backends/smt2/smtio.py

@@ -704,6 +704,8 @@ class SmtIo:
                     if msg is not None:
                         print("%s waiting for solver (%s)" % (self.timestamp(), msg), flush=True)
 
+        result = ""
+        while result not in ["sat", "unsat", "unknown"]:
             result = self.read()
 
         if self.debug_file: