This enables the execution of the acceptance tests on Travis.

Because the Travis environment is based on Ubuntu Trusty, it requires
the python3-pip and python3.4-venv packages.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Reviewed-by: Caio Carrara <ccarrara@redhat.com>
Message-Id: <20181018153134.8493-4-crosa@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>