Install celery 3 on the master branch travis.yml

issue #109

.travis.yml

@@ -24,7 +24,7 @@ before_install:
   # Celery
   - sudo apt-get install -y python-virtualenv
   - virtualenv venv
-  - venv/bin/pip install celery redis
+  - venv/bin/pip install 'celery<4' redis
   - venv/bin/celery worker --config celeryamqplibconfig --workdir $PWD/testscenario --detach --pidfile celeryamqplib.pid
   - venv/bin/celery worker --config celerypeclconfig --workdir $PWD/testscenario --detach --pidfile celerypecl.pid
   - venv/bin/celery worker --config celeryredisconfig --workdir $PWD/testscenario --detach --pidfile celeryredis.pid