Update pytest from 3.4.0 to 3.4.1

requirements.txt

 psutil==5.4.3
 py==1.5.2
 pyglet==1.3.1
-pytest==3.4.0
+pytest==3.4.1
 python-dateutil==2.6.1
 PyYAML==3.12
 redis==2.10.6