Update dockerflow from 2019.5.0 to 2019.6.0

requirements/prod.txt

@@ -204,9 +204,9 @@ djangorestframework==3.9.4 \
 djangorestframework-jwt==1.11.0 \
     --hash=sha256:ab15dfbbe535eede8e2e53adaf52ef0cf018ee27dbfad10cbc4cbec2ab63d38c \
     --hash=sha256:5efe33032f3a4518a300dc51a51c92145ad95fb6f4b272e5aa24701db67936a7
-dockerflow==2019.5.0 \
-    --hash=sha256:1beb894ccdb28e022f61086b1117ae0e38790f18abfe90c782f249af1aa2442a \
-    --hash=sha256:8c4ffdad72732b16409b6a5599ef338c845e28aac902d09008bb8fae17a157a3
+dockerflow==2019.6.0 \
+    --hash=sha256:3342654c419492fa16dc5872546c893433fefce8fd9ba90da9bc9cfcafaecac1 \
+    --hash=sha256:885e4e32ebedc87a86c0d9c16fe4797f9ffe70622eb3a056615e37611eb983fd
 drf-nested-routers==0.91 \
     --hash=sha256:60c1e1f5cc801e757d26a8138e61c44419ef800c213c3640c5b6138e77d46762 \
     --hash=sha256:46e5c3abc15c782cafafd7d75028e8f9121bbc6228e3599bbb48a3daa4585034