fix code review findings

Author: Helene

source/metaclasses.py

@@ -26,4 +26,4 @@ class Singleton(type):
     def __call__(cls, *args, **kwargs):
         if cls not in cls._instances:
             cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
-        return cls._instances[cls]
+        return cls._instances[cls]

tests/test_metadatahandler.py

@@ -1,5 +1,4 @@
 import os
-import sys
 from source.bridgeLogger import configureLogging
 from source.zimonGrafanaIntf import MetadataHandler
 from nose2.tools.such import helper as assert_helper
@@ -19,18 +18,18 @@ def my_setup():
 @with_setup(my_setup)
 def test_case01():
     with assert_helper.assertRaises(KeyError):
-        md=MetadataHandler()
+        MetadataHandler()
 
 
 @with_setup(my_setup)
 def test_case02():
     with assert_helper.assertRaises(KeyError):
-        md=MetadataHandler(logger=logger, apiKeyName='scale_grafana')
+        MetadataHandler(logger=logger, apiKeyName='scale_grafana')
 
 @with_setup(my_setup)
 def test_case03():
     with assert_helper.assertRaises(KeyError):
-        md=MetadataHandler(logger=logger, server='localhost', port='4242', apiKeyName='scale_grafana')
+        MetadataHandler(logger=logger, server='localhost', port='4242', apiKeyName='scale_grafana')
 
 
 @with_setup(my_setup)
@@ -41,4 +40,3 @@ def test_case04():
         assert md == md1
         assert md1.logger == logger
         assert md1.apiKeyName == 'scale_grafana'
-