Try to use container image from DockerHub

scripts/travis-test.sh

@@ -1,7 +1,8 @@
 #!/usr/bin/env bash
 
 docker exec -i devstack /bin/bash -s <<EOF
-git clone -b oxa/devfic https://github.com/Microsoft/edx-theme.git /edx/app/edxapp/themes
+git clone -b oxa/devfic https://github.com/Microsoft/edx-theme.git /tmp/edx-theme
+cp -r -u /tmp/edx-theme /edx/app/edxapp/themes
 sudo su edxapp
 source /edx/app/edxapp/edxapp_env
 cd /edx/app/edxapp/edx-platform