Update frontend Dockerfile

Debian stretch apt repositories have been archived.  This PR allows the frontend  Dockerfile to continue to be built.

Author: manugarri

frontend/Dockerfile

@@ -1,6 +1,8 @@
 FROM node:10.15.3-stretch
 
 # AWS cli tools
+# Debian stretch repositories have been archived. We need to change the sources
+RUN echo "deb http://archive.debian.org/debian stretch main" > /etc/apt/sources.list
 RUN apt-get update && apt-get install -y \
     build-essential \
     python \