Set noninteractive so tests don't hang

test/Dockerfile-ubuntu

@@ -2,6 +2,9 @@ FROM ubuntu:latest
 
 # Note this image uses mawk1.3
 
+# Set noninteractive otherwise tzdata hangs
+ENV DEBIAN_FRONTEND noninteractive
+
 # Update and install required software
 RUN apt-get update --fix-missing
 RUN apt-get install -y git curl dnsutils wget nginx-light

test/Dockerfile-ubuntu-staging

@@ -2,8 +2,13 @@ FROM ubuntu:latest
 
 # Note this image uses mawk1.3
 
+# Set noninteractive otherwise tzdata hangs
+ENV DEBIAN_FRONTEND noninteractive
+
+# Ensure tests in this image use the staging server
 ENV staging "true"
 ENV DUCKDNS_TOKEN 1d616aa9-b8e4-4bb4-b312-3289de82badb
+
 # Update and install required software
 RUN apt-get update --fix-missing
 RUN apt-get install -y git curl dnsutils wget nginx-light