From 8c75da916c7be82e6e6ad6a83f48aa8416d806f8 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Date: Fri, 22 May 2020 10:17:47 +0100
Subject: [PATCH] Refresh apt cache when building dh_virtualenv docker image
 (#7555)

When we tried to build debs for 1.13.0, the build failed because docker used a
base docker image which had a stale apt cache.

Fixes: #7540
---
 changelog.d/7555.misc          | 1 +
 docker/Dockerfile-dhvirtualenv | 6 ++++--
 2 files changed, 5 insertions(+), 2 deletions(-)
 create mode 100644 changelog.d/7555.misc

diff --git a/changelog.d/7555.misc b/changelog.d/7555.misc
new file mode 100644
index 0000000000..75a3176133
--- /dev/null
+++ b/changelog.d/7555.misc
@@ -0,0 +1 @@
+Refresh apt cache when building dh_virtualenv docker image.
diff --git a/docker/Dockerfile-dhvirtualenv b/docker/Dockerfile-dhvirtualenv
index 579724685c..bf6af74104 100644
--- a/docker/Dockerfile-dhvirtualenv
+++ b/docker/Dockerfile-dhvirtualenv
@@ -31,8 +31,10 @@ RUN mkdir /dh-virtualenv
 RUN wget -q -O /dh-virtualenv.tar.gz https://github.com/matrix-org/dh-virtualenv/archive/matrixorg-20200519.tar.gz
 RUN tar -xv --strip-components=1 -C /dh-virtualenv -f /dh-virtualenv.tar.gz
 
-# install its build deps
-RUN cd /dh-virtualenv \
+# install its build deps. We do another apt-cache-update here, because we might
+# be using a stale cache from docker build.
+RUN apt-get update -qq -o Acquire::Languages=none \
+    && cd /dh-virtualenv \
     && env DEBIAN_FRONTEND=noninteractive mk-build-deps -ri -t "apt-get -y --no-install-recommends"
 
 # build it