Update psutil from 5.4.1 to 5.4.2

requirements.txt

@@ -5,7 +5,7 @@ freezegun==0.3.9
 future==0.16.0
 numpy==1.13.3
 pluggy==0.6.0
-psutil==5.4.1
+psutil==5.4.2
 py==1.5.2
 pyglet==1.3.0
 pytest==3.3.0