tests/topotests: Set -o cache_dir=/tmp

We are mounting the topotests from the host into the container
and mark them as read-only to avoid any modifications to the host.

Pytest tries to create a .pytest_chache directory in that location
which fails because of the read-only mount.

Configure a different cache dir which is writable to resolve this.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>

tests/topotests/docker/inner/entrypoint.sh

@@ -40,7 +40,10 @@ chmod 1777 /tmp
 if [ $# -eq 0 ] || ([[ "$1" != /* ]] && [[ "$1" != ./* ]]); then
 	export TOPOTESTS_CHECK_MEMLEAK=/tmp/memleak_
 	export TOPOTESTS_CHECK_STDERR=Yes
-	set -- pytest --junitxml /tmp/topotests.xml "$@"
+	set -- pytest \
+		--junitxml /tmp/topotests.xml \
+		-o cache_dir=/tmp \
+		"$@"
 fi
 
 exec "$@"