added pylint to image

Dockerfile.buster

@@ -3,4 +3,5 @@ FROM debian:buster
 RUN apt-get -qq update && \
     apt-get -qq dist-upgrade && \
     apt-get -qq install sqlite3 locales-all git python3 python3-coverage python3-ldap3 python3-flask python3-flask-sqlalchemy lsb-release python3-pip && \
+    pip3 install pylint && \
     apt-get -qq clean