Update pytest from 3.0.7 to 3.1.2 (#2546)

Author: pyup-bot

requirements/dev.txt

@@ -1,8 +1,8 @@
 # Dependencies needed only for development/testing.
 
-pytest==3.0.7 \
-    --hash=sha256:66f332ae62593b874a648b10a8cb106bfdacd2c6288ed7dec3713c3a808a6017 \
-    --hash=sha256:b70696ebd1a5e6b627e7e3ac1365a4bc60aaf3495e843c1e70448966c5224cab
+pytest==3.1.2 \
+    --hash=sha256:41e618f317957505ae2e81935733d8304d84170f7e21dfb15184d6fa8d7a5230 \
+    --hash=sha256:795ec29fbba70b22a593691ce8bcd4bdde2dc96e8099731f73c7d8bb3ce879bf
 
 django-debug-toolbar==1.8 \
     --hash=sha256:e9f08b94f9423ac76cfc287151182bbaddbe7521ae32bef9f9863e2ac58018d3 \