Suppress the output from sentiment analysis

.travis.yml

@@ -75,7 +75,7 @@ script:
   - (cd contrib/_plugin_example && make)
   - $GOPATH/bin/hercules --burndown --burndown-files --burndown-people --couples --quiet https://github.com/src-d/hercules | python3 labours.py -m all -o out --backend Agg --disable-projector
   - $GOPATH/bin/hercules --burndown --burndown-files --burndown-people --couples --quiet --pb https://github.com/src-d/hercules | python3 labours.py -f pb -m all -o out --backend Agg --disable-projector
-  - $GOPATH/bin/hercules --sentiment --quiet --languages Python https://github.com/src-d/hercules
+  - $GOPATH/bin/hercules --sentiment --quiet --languages Python https://github.com/src-d/hercules > /dev/null
   - set +e
   - if [[ $TRAVIS_GO_VERSION = 1.10.* ]]; then bash <(curl -s https://codecov.io/bash); fi