Added warning message to nvidia_smi xmldevicequery

I think this was only ever meant to be an example in the original nvml
library. Given that nvidia update the nvidia smi query, it will be too
hard to keep this query up to date. Instead, calling 'nvidia-smi -q -x'
from python with subprocess would achieve the same result.

Author: fbcotter

py3nvml/nvidia_smi.py

@@ -41,6 +41,9 @@
 
 from .py3nvml import *
 import datetime
+import warnings
+import logging
+import os
 
 #
 # Helper functions
@@ -200,6 +203,10 @@ def handleError(err):
 
 #######
 def XmlDeviceQuery():
+    logger = logging.getLogger(__name__)
+    str_ = """Warning this function is deprecated and will be removed in future releases."""
+    warnings.warn(str_, RuntimeWarning)
+    logger.warn(str_)
 
     strResult = ''
     try: