deps: update pytest from 4.0.2 to 4.1.0

Update pytest from 4.0.2 to 4.1.0 (#21)

requirements.txt

@@ -1,4 +1,4 @@
 mock==2.0.0
 pylint==1.9.3
-pytest==4.0.2
+pytest==4.1.0
 snapshottest==0.5.0