[PULL 17/25] python/qemu/qtest: Check before accessing _qtest

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

From: John Snow <jsnow@redhat.com>

It can be None; so add assertions or exceptions where appropriate to
guard the access accordingly.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200514055403.18902-30-jsnow@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 python/qemu/qtest.py | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/python/qemu/qtest.py b/python/qemu/qtest.py
index 4c88590eb0..888c8bd2f6 100644
--- a/python/qemu/qtest.py
+++ b/python/qemu/qtest.py
@@ -121,7 +121,8 @@ def _pre_launch(self):
         super()._pre_launch()
         self._qtest = QEMUQtestProtocol(self._qtest_path, server=True)
 
-    def _post_launch(self):
+    def _post_launch(self) -> None:
+        assert self._qtest is not None
         super()._post_launch()
         self._qtest.accept()
 
@@ -129,6 +130,13 @@ def _post_shutdown(self):
         super()._post_shutdown()
         self._remove_if_exists(self._qtest_path)
 
-    def qtest(self, cmd):
-        '''Send a qtest command to guest'''
+    def qtest(self, cmd: str) -> str:
+        """
+        Send a qtest command to the guest.
+
+        :param cmd: qtest command to send
+        :return: qtest server response
+        """
+        if self._qtest is None:
+            raise RuntimeError("qtest socket not available")
         return self._qtest.cmd(cmd)
-- 
2.21.3