travis: add sphinx to trigger doc build

diff --git a/.travis.yml b/.travis.yml
index ae1523f53c1491fb783eaf19c163389fb8334fe6..d6c15faf805d209750f7cc92a174c1d981d3b5ce 100644 (file)
--- a/.travis.yml
+++ b/.travis.yml
@@ -105,6 +105,7 @@ matrix:
             - *packages
             - coccinelle
             - gcc-7
+            - python3-sphinx
     # Linux, gcc, Rust (latest stable).
     # This is allowed to fail, update allow_failures if the env changes.
     - os: linux