Update package versions to 2019.2.15 and fix flake8

Change-Id: I491a6f23065189390f7287b1ce756ac5e88d2b99
diff --git a/cfg_checker/nodes.py b/cfg_checker/nodes.py
index eea6500..fde217f 100644
--- a/cfg_checker/nodes.py
+++ b/cfg_checker/nodes.py
@@ -39,7 +39,7 @@
                     "\n".join(_invalid)
                 )
             )
-        
+
     # process wildcard, create node list out of mask
     if skip_list:
         _list = []