scripts: Remove debug parameter from QEMUMonitorProtocol

Use logging module for the QMP debug messages.  The only scripts
that set debug=True are iotests.py and guestperf/engine.py, and
they already call logging.basicConfig() to set up logging.

Scripts that don't configure logging are safe as long as they
don't need debugging output, because debug messages don't trigger
the "No handlers could be found for logger" message from the
Python logging module.

Scripts that already configure logging but don't use debug=True
(e.g. scripts/vm/basevm.py) will get QMP debugging enabled for
free.

Cc: "Alex Bennée" <alex.bennee@linaro.org>
Cc: Fam Zheng <famz@redhat.com>
Cc: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20171005172013.3098-3-ehabkost@redhat.com>
Reviewed-by: Lukáš Doktor <ldoktor@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

scripts/qemu.py

@@ -177,8 +177,7 @@ def _base_args(self):
 
     def _pre_launch(self):
         self._qmp = qmp.qmp.QEMUMonitorProtocol(self._monitor_address,
-                                                server=True,
-                                                debug=self._debug)
+                                                server=True)
 
     def _post_launch(self):
         self._qmp.accept()

scripts/qmp/qmp.py

@@ -11,7 +11,7 @@
 import json
 import errno
 import socket
-import sys
+import logging
 
 
 class QMPError(Exception):
@@ -32,12 +32,14 @@ class QMPTimeoutError(QMPError):
 
 class QEMUMonitorProtocol(object):
 
+    #: Logger object for debugging messages
+    logger = logging.getLogger('QMP')
     #: Socket's error class
     error = socket.error
     #: Socket's timeout
     timeout = socket.timeout
 
-    def __init__(self, address, server=False, debug=False):
+    def __init__(self, address, server=False):
         """
         Create a QEMUMonitorProtocol class.
 
@@ -51,7 +53,6 @@ def __init__(self, address, server=False, debug=False):
         """
         self.__events = []
         self.__address = address
-        self._debug = debug
         self.__sock = self.__get_sock()
         self.__sockfile = None
         if server:
@@ -83,8 +84,7 @@ def __json_read(self, only_event=False):
                 return
             resp = json.loads(data)
             if 'event' in resp:
-                if self._debug:
-                    print >>sys.stderr, "QMP:<<< %s" % resp
+                self.logger.debug("<<< %s", resp)
                 self.__events.append(resp)
                 if not only_event:
                     continue
@@ -164,8 +164,7 @@ def cmd_obj(self, qmp_cmd):
         @return QMP response as a Python dict or None if the connection has
                 been closed
         """
-        if self._debug:
-            print >>sys.stderr, "QMP:>>> %s" % qmp_cmd
+        self.logger.debug(">>> %s", qmp_cmd)
         try:
             self.__sock.sendall(json.dumps(qmp_cmd))
         except socket.error as err:
@@ -173,8 +172,7 @@ def cmd_obj(self, qmp_cmd):
                 return
             raise socket.error(err)
         resp = self.__json_read()
-        if self._debug:
-            print >>sys.stderr, "QMP:<<< %s" % resp
+        self.logger.debug("<<< %s", resp)
         return resp
 
     def cmd(self, name, args=None, cmd_id=None):