Make Vagrant disk larger for running tests

Vagrantfile

@@ -26,13 +26,28 @@
 # backwards compatibility). Please don't change it unless you know what
 # you're doing.
 Vagrant.configure(2) do |config|
+  required_plugins = %w( vagrant-vbguest vagrant-disksize )
+  _retry = false
+  required_plugins.each do |plugin|
+    unless Vagrant.has_plugin? plugin
+      system "vagrant plugin install #{plugin}"
+      _retry=true
+    end
+  end
+
+  if (_retry)
+    exec "vagrant " + ARGV.join(' ')
+  end
+
+
   # The most common configuration options are documented and commented below.
   # For a complete reference, please see the online documentation at
   # https://docs.vagrantup.com.
 
   # Every Vagrant development environment requires a box. You can search for
   # boxes at https://atlas.hashicorp.com/search.
   config.vm.box = "ubuntu/xenial64"
+  config.disksize.size = "20GB"
 
   # 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,