python/qemu/qmp.py: Preserve error context on re-raise

Use the "from ..." phrasing when re-raising errors to preserve their
initial context, to help aid debugging when things go wrong.

This also silences a pylint 2.6.0+ error.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 20201006235817.3280413-18-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py
index 9223307ed81b349bff76a9119f75b6051d80875b..d911999da1fdb26c4da6aaeefd4b26ac6b927e9e 100644 (file)
--- a/python/qemu/qmp.py
+++ b/python/qemu/qmp.py
@@ -181,10 +181,11 @@ class QEMUMonitorProtocol:
                 self.__sock.settimeout(wait)
             try:
                 ret = self.__json_read(only_event=True)
-            except socket.timeout:
-                raise QMPTimeoutError("Timeout waiting for event")
-            except:
-                raise QMPConnectError("Error while reading from socket")
+            except socket.timeout as err:
+                raise QMPTimeoutError("Timeout waiting for event") from err
+            except Exception as err:
+                msg = "Error while reading from socket"
+                raise QMPConnectError(msg) from err
             if ret is None:
                 raise QMPConnectError("Error while reading from socket")
             self.__sock.settimeout(None)