Update docker image to alpine 3.10

Dockerfile

-FROM docker.io/alpine:3.9
+FROM docker.io/alpine:3.10
 
 ENV UID=1337 \
     GID=1337
@@ -11,8 +11,7 @@ RUN apk add --no-cache \
       py3-magic \
       py3-sqlalchemy \
       py3-psycopg2 \
-      # Not yet in stable repos:
-      #py3-ruamel.yaml \
+      py3-ruamel.yaml \
       # Indirect dependencies
       #commonmark
         py3-future \