We always install the same packages ever and ever, cache them.

See https://docs.travis-ci.com/user/caching/#pip-cache

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 .travis.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.travis.yml b/.travis.yml
index a65d13a592..3211667adb 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,6 +8,7 @@ compiler:
 cache:
   timeout: 1200
   ccache: true
+  pip: true
 
 
 addons:
-- 
2.20.1