ascn container: apt-get install failed

Does this help?

container/Dockerfile.ascn

 ARG CI_REGISTRY_IMAGE
 FROM $CI_REGISTRY_IMAGE/varnish-ingress/klarlack:master
 
+RUN apt-get update && \
+	apt-get upgrade -y
+
 # watermark related
 RUN apt-get install -y \
     gcc git \
@@ -36,6 +39,12 @@ RUN git clone https://code.uplex.de/misc/elbestream.git && \
     cd .. && \
     rm -rf elbestream
 
+RUN apt-get autoremove -y -q && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/* && \
+    rm -rf /usr/share/doc && \
+    rm -rf /usr/share/man
+
 ENV HTTP_PORT=8888 PROTO=HTTP READY_PORT=8080 SECRET_PATH=/var/run/varnish \
     SECRET_FILE=_.secret ADMIN_PORT=6081 GROUP=varnish \
     OFFLOAD_PATH=/var/run/offload/varnish.sock CONFIG_PORT=8000