Avocado tests download artifacts from various sources.
These sources sometime have network issues resulting in build
failures. Cache Avocado cache to reduce build failure.

See https://docs.travis-ci.com/user/caching/#arbitrary-directories

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 .travis.yml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/.travis.yml b/.travis.yml
index 3211667adb..a3db5b3f63 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,6 +9,8 @@ cache:
   timeout: 1200
   ccache: true
   pip: true
+  directories:
+  - $HOME/avocado/data/cache
 
 
 addons:
-- 
2.20.1