Improve posix error code message

mjtest/util/shell.py

@@ -4,6 +4,7 @@
 Convenience function
 Alternative to subprocess and os.system
 """
+import os
 import shlex
 import subprocess
 has_resource_module = True
@@ -113,7 +114,7 @@ class _Execute(object):
             self.returncode = 128 - self.returncode
         if self.returncode in _EXIT_CODES:
             _LOG.debug("returncode %d recognized as '%s'" % (self.returncode, _EXIT_CODES[self.returncode]))
-            raise SigKill(self.returncode, _EXIT_CODES[self.returncode])
+            raise SigKill(-self.returncode, _EXIT_CODES[self.returncode] + ": " + os.strerror(-self.returncode))
         return (self.out, self.err, self.returncode)
 
 def execute(cmd, env=None, timeout=0, rlimit=None, propagate_sigint=True):