Upgrade Debian image to buster

Dockerfile

-FROM debian:stretch
+FROM debian:buster
 
 ARG IGNORE_EXPIRY=0
 ENV LANG=C.UTF-8

install.sh

@@ -3,10 +3,10 @@ set -e
 set -x
 
 # use snapshot repos for deterministic package versions
-DATE="20191003T000000Z"
+DATE="20191004T000000Z"
 cat << EOF > /etc/apt/sources.list
-deb http://snapshot.debian.org/archive/debian/${DATE}/ stretch main
-deb http://snapshot.debian.org/archive/debian-security/${DATE}/ stretch/updates main
+deb http://snapshot.debian.org/archive/debian/${DATE}/ buster main
+deb http://snapshot.debian.org/archive/debian-security/${DATE}/ buster/updates main
 EOF
 
 # ignore expired package releases if env variable is set
@@ -16,7 +16,7 @@ then
 fi
 
 # update package sources
-apt-get update
+apt-get update --allow-releaseinfo-change
 apt-get -y upgrade
 
 # do not install documentation to keep image small