Exit code fix

Author: boxed

mutmut/__main__.py

@@ -73,6 +73,7 @@
 status_by_exit_code = {
     1: 'killed',
     3: 'killed',  # internal error in pytest means a kill
+    -24: 'killed',
     0: 'survived',
     5: 'no tests',
     2: 'check was interrupted by user',