Update py from 1.5.2 to 1.5.3

requirements.txt

 numpy==1.14.2
 pluggy==0.6.0
 psutil==5.4.3
-py==1.5.2
+py==1.5.3
 pyglet==1.3.1
 pytest==3.4.2
 python-dateutil==2.7.0