Merge ~d0ugal/maas-images:sitepackages-sadpanda into maas-images:master

[Dougal Matthews]

Use sitepackages=true to get a more recent distro_info

[Adam Collard (adam-collard)]

review: Approve

diff --git a/.gitignore b/.gitignore
index bee8a64..723482a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,3 @@
 __pycache__
+.tox
+MANIFEST
diff --git a/tox.ini b/tox.ini
index 45c88a0..b1ab5a8 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,10 +4,10 @@ recreate = False
 
 [testenv]
 basepython=python3
+sitepackages=true
 deps =
      git+https://git.launchpad.net/simplestreams
      pyyaml
-     distro_info
 
 setenv =
     LC_ALL = C