Updated vm_mhz_to_percentage, return [0] if there are no VMs - the host is idle

neat/locals/manager.py

@@ -431,6 +431,9 @@ def vm_mhz_to_percentage(vm_mhz_history, host_mhz_history, physical_cpu_mhz):
     :return: The history of the host's CPU utilization in percentages.
      :rtype: list(float)
     """
+    if not vm_mhz_history:
+        return [0.]
+
     max_len = max(len(x) for x in vm_mhz_history)
     if len(host_mhz_history) > max_len:
         host_mhz_history = host_mhz_history[-max_len:]

tests/locals/test_manager.py

@@ -196,3 +196,9 @@ class LocalManager(TestCase):
             3000),
             [0.1, 0.2, 0.2, 0.5])
 
+        self.assertEqual(manager.vm_mhz_to_percentage(
+            [],
+            [300, 0, 300, 0, 300],
+            3000),
+            [0.])
+