Fix black issues and run tox properly in stage-test

Change-Id: Ie08f3029df03f97f1df1461a564c24ce024974fe
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/tox.ini b/tox.ini
index f1aeb9b..b014de1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -27,6 +27,7 @@
 setenv = VIRTUAL_ENV={envdir}
          PYTHONDONTWRITEBYTECODE = 1
 deps =  -r{toxinidir}/requirements.txt
+parallel_show_output = true
 
 #######################################################################################
 [testenv:black]