scripts/qmp-shell: use logging to show warnings

A perfect candidate is non-fatal shell history messages.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 20210607200649.1840382-33-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

scripts/qmp/qmp-shell

@@ -67,6 +67,7 @@
 import argparse
 import ast
 import json
+import logging
 import os
 import re
 import readline
@@ -85,6 +86,9 @@ from qemu import qmp
 from qemu.qmp import QMPMessage
 
 
+LOG = logging.getLogger(__name__)
+
+
 class QMPCompleter:
     # NB: Python 3.9+ will probably allow us to subclass list[str] directly,
     # but pylint as of today does not know that List[str] is simply 'list'.
@@ -167,13 +171,15 @@ class QMPShell(qmp.QEMUMonitorProtocol):
         except FileNotFoundError:
             pass
         except IOError as err:
-            print(f"Failed to read history '{self._histfile}': {err!s}")
+            msg = f"Failed to read history '{self._histfile}': {err!s}"
+            LOG.warning(msg)
 
     def _save_history(self) -> None:
         try:
             readline.write_history_file(self._histfile)
         except IOError as err:
-            print(f"Failed to save history file '{self._histfile}': {err!s}")
+            msg = f"Failed to save history file '{self._histfile}': {err!s}"
+            LOG.warning(msg)
 
     @classmethod
     def __parse_value(cls, val: str) -> object: