python/qmp.py: re-absorb MonitorResponseError

When I initially split this out, I considered this more of a machine
error than a QMP protocol error, but I think that's misguided.

Move this back to qmp.py and name it QMPResponseError. Convert
qmp.command() to use this exception type.

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: <20200710052220.3306-4-jsnow@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
diff --git a/python/qemu/machine.py b/python/qemu/machine.py
index 6905518..80c4d4a 100644
--- a/python/qemu/machine.py
+++ b/python/qemu/machine.py
@@ -56,19 +56,6 @@
     """
 
 
-class MonitorResponseError(qmp.QMPError):
-    """
-    Represents erroneous QMP monitor reply
-    """
-    def __init__(self, reply):
-        try:
-            desc = reply["error"]["desc"]
-        except KeyError:
-            desc = reply
-        super().__init__(desc)
-        self.reply = reply
-
-
 class QEMUMachine:
     """
     A QEMU VM
@@ -533,7 +520,7 @@
         if reply is None:
             raise qmp.QMPError("Monitor is closed")
         if "error" in reply:
-            raise MonitorResponseError(reply)
+            raise qmp.QMPResponseError(reply)
         return reply["return"]
 
     def get_qmp_event(self, wait=False):