update to debian 9

Dockerfile

@@ -1,9 +1,10 @@
-FROM debian8_python3
+FROM debian:9
 
 MAINTAINER Joachim Lusiardi
 
 RUN apt-get update; \
     apt-get install -y \
+        python3-pip \
         git \
         haproxy; \
     git clone https://github.com/letsencrypt/letsencrypt ;\