[modules/sensors] Add fallback for temperature retrieval

If /sys/class/ data cannot be read, fall back to "sensors -u", by
popular demand :P

see #145

README.md

@@ -123,6 +123,7 @@ Modules and commandline utilities are only required for modules, the core itself
 * bluez / blueman (for module 'bluetooth')
 * dbus-send (for module 'bluetooth')
 * nvidia-smi (for module 'nvidiagpu')
+* sensors (for module 'sensors', as fallback)
 
 # Examples
 Here are some screenshots for all themes that currently exist:

bumblebee/modules/sensors.py

@@ -5,27 +5,45 @@
 
 Parameters:
     * sensors.path: path to temperature file (default /sys/class/thermal/thermal_zone0/temp).
+    * sensors.match: (fallback) Line to match against output of 'sensors -u' (default: temp1_input)
+    * sensors.match_number: (fallback) which of the matches you want (default -1: last match).
+
 """
 
 import re
+import logging
 
+import bumblebee.util
 import bumblebee.input
 import bumblebee.output
 import bumblebee.engine
 
+log = logging.getLogger(__name__)
+
 class Module(bumblebee.engine.Module):
     def __init__(self, engine, config):
         super(Module, self).__init__(engine, config,
                                      bumblebee.output.Widget(full_text=self.temperature))
         self._temperature = "unknown"
         self._mhz = "n/a"
+        self._match_number = int(self.parameter("match_number", "-1"))
+        self._pattern = re.compile(r"^\s*{}:\s*([\d.]+)$".format(self.parameter("match", "temp1_input")), re.MULTILINE)
         engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE, cmd="xsensors")
 
+    def _get_temp_from_sensors(self):
+        output = bumblebee.util.execute("sensors -u")
+        match = self._pattern.findall(output)
+        if match:
+            return int(float(match[self._match_number]))
+        return "unknown"
+
     def get_temp(self):
         try:
             temperature = open(self.parameter("path", "/sys/class/thermal/thermal_zone0/temp")).read()[:2]
+            log.debug("retrieved temperature from /sys/class/")
         except IOError:
-            temperature = "unknown"
+            temperature = self._get_temp_from_sensors()
+            log.debug("retrieved temperature from 'sensors -u'")
         return temperature
 
     def get_mhz( self ):