power_Consumption: fix type error

This fixes a type error with SystemPower which needs to be wrapped in
a list.

TEST=power_Consumption
BUG=None

Change-Id: Id96f9f0c9ed04a12e7b0b3b610beb5404c18957f
Reviewed-on: https://chromium-review.googlesource.com/550949
Commit-Ready: Derek Basehore <dbasehore@chromium.org>
Tested-by: Derek Basehore <dbasehore@chromium.org>
Reviewed-by: Eric Caruso <ejcaruso@chromium.org>
diff --git a/client/site_tests/power_Consumption/power_Consumption.py b/client/site_tests/power_Consumption/power_Consumption.py
index e80293a..36341d7 100644
--- a/client/site_tests/power_Consumption/power_Consumption.py
+++ b/client/site_tests/power_Consumption/power_Consumption.py
@@ -471,7 +471,8 @@
 
         measure = []
         if not self._power_status.on_ac():
-            measure += power_status.SystemPower(self._power_status.battery_path)
+            measure += \
+                [power_status.SystemPower(self._power_status.battery_path)]
         if power_utils.has_rapl_support():
             measure += power_rapl.create_rapl()
         self._plog = power_status.PowerLogger(measure)