tests: use more recent Yunohost box

Vagrantfile

@@ -11,11 +11,23 @@ Vagrant.configure("2") do |config|
   # https://docs.vagrantup.com.
 
   config.vm.define :ynhtests
-  config.vm.box = "yunohost/jessie-stable"
+  config.vm.box = "yunohost-stretch-unstable"
+  config.vm.box_url = "https://build.yunohost.org/yunohost-stretch-unstable.box"
 
   # Disable auto updates checks. Run `vagrant outdated` to perform manual updates.
   config.vm.box_check_update = false
 
+  # Configuration for the vagrant-disksize plugin.
+  # We need more space because package_check will create many LXC containers and snapshots.
+  #
+  # IMPORTANT: when re-creating the VM from scratch, the logical size of the disk will
+  # still be 10 Go.
+  # You'll need a live GParted ISO to resize partitions and fix it.
+  config.disksize.size = '20GB'
+
+  # Force guest type, because YunoHost /etc/issue can't be tuned
+  config.vm.guest = :debian
+
   # Create a forwarded port mapping which allows access to a specific port
   # within the machine from a port on the host machine. In the example below,
   # accessing "localhost:8080" will access port 80 on the guest machine.

test.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
 # Run package_check tests against the app in the working directory on a Vagrant virtual machine.
+#
+# NB: Vagrant is used because package_check uses LXC containers, and Docker doesn't support running LXC.
 
 # Fail on first error
 set -e