Adds pylint to tox test pipeline and fixes related errors

Change-Id: I0965b2818898d144a441208391f4c831fa28279b
Signed-off-by: Benjamin Diaz <bdiaz@whitestack.com>
diff --git a/osm_mon/evaluator/evaluator.py b/osm_mon/evaluator/evaluator.py
index 90c0c17..24e8e43 100644
--- a/osm_mon/evaluator/evaluator.py
+++ b/osm_mon/evaluator/evaluator.py
@@ -77,7 +77,7 @@
             json_response = r.json()
             if json_response['status'] == 'success':
                 result = json_response['data']['result']
-                if len(result):
+                if result:
                     metric_value = float(result[0]['value'][1])
                     log.info("Metric value: %s", metric_value)
                     if alarm.operation.upper() == 'GT':