Fix: pytest 5.0.0 issue that breaks installs

Change-Id: Ice3cddc4083b23e5c9d148c3ddea98c7a982f46f
Signed-off-by: peusterm <manuel.peuster@uni-paderborn.de>
diff --git a/setup.py b/setup.py
index 7442fda..ef1f0fe 100755
--- a/setup.py
+++ b/setup.py
@@ -47,7 +47,7 @@
           'six>=1.9',
           'ryu',
           'oslo.config',
-          'pytest',
+          'pytest<=4.6.4',
           'Flask',
           'flask_restful',
           'docker==2.0.2',
@@ -70,5 +70,5 @@
           ],
       },
       setup_requires=['pytest-runner'],
-      tests_require=['pytest', 'more-itertools<=5.0.0'],
+      tests_require=['pytest<=4.6.4', 'more-itertools<=5.0.0'],
       )