collect: tolerate "No sensors found!" error running sensors

/reviewed-on !81

slapos/collect/temperature/__init__.py

 from __future__ import print_function
 
 from multiprocessing import Process, active_children, cpu_count, Pipe
-import subprocess
+try:
+  import subprocess32 as subprocess
+except ImportError:
+  import subprocess
 import os
 import signal
 import sys
@@ -15,9 +18,18 @@ except NotImplementedError:
     DEFAULT_CPU = 1
 
 def collectComputerTemperature(sensor_bin="sensors"):
-  stdout = subprocess.check_output((sensor_bin, '-u'), universal_newlines=True)
-
-  sensor_output_list = stdout.splitlines()
+  result = subprocess.run((sensor_bin, '-u'),
+                          universal_newlines=True,
+                          stdout=subprocess.PIPE,
+                          stderr=subprocess.STDOUT)
+
+  if result.returncode:
+    # This can happen on environments where sensors are not available,
+    # such as virtual machines.
+    if "No sensors found!" not in result.stdout:
+      raise RuntimeError("Error executing {}: {}".format(sensor_bin, result.stdout))
+
+  sensor_output_list = result.stdout.splitlines()
   adapter_name = ""
   
   sensor_temperature_list = []

[Nicolas Wavrant]

This may fail depending of the localization set on the server. Can this test be based on a returncode instead ?

[Jérome Perrin]

Good point. In the version we are using, there's no translation apparently (not here for 3.3.5 also not on master), so it seems OK for now.

The rest of this function also parse the output, so it's vulnerable from the same problem.

In the discussions on 7467ef4c (comment 71574) slapos!479 (merged) and !81 (merged) we also said that rather than parsing output like this we could use psutil (but I don't think anybody confirmed we'll do this).