Fix typo in run_command (#810)

diff --git a/mobly/utils.py b/mobly/utils.py
index 6015617..8140d28 100644
--- a/mobly/utils.py
+++ b/mobly/utils.py
@@ -477,7 +477,7 @@
   if timer is not None:
     timer.cancel()
   if timer_triggered.is_set():
-    raise subprocess.TimeoutExpired(cmd=cwd,
+    raise subprocess.TimeoutExpired(cmd=cmd,
                                     timeout=timeout,
                                     output=out,
                                     stderr=err)
diff --git a/tests/mobly/utils_test.py b/tests/mobly/utils_test.py
index 16204c9..7e95718 100755
--- a/tests/mobly/utils_test.py
+++ b/tests/mobly/utils_test.py
@@ -223,7 +223,7 @@
     self.assertEqual(ret, 0)
 
   def test_run_command_with_timeout_expired(self):
-    with self.assertRaises(subprocess.TimeoutExpired):
+    with self.assertRaisesRegex(subprocess.TimeoutExpired, 'sleep'):
       _ = utils.run_command(self.sleep_cmd(4), timeout=0.01)
 
   @mock.patch('threading.Timer')