A couple of things wrong with this. The biggest problem is that your SQLAlchemy is a regression to an older version of this package, and it looks like you regressed more than the version number on that slackbuild. Why?
Another thing is your Django.SlackBuild already has the slack-desc text inside it, and you also have a slack-desc file. When you write the description inside the SlackBuild, a slack-desc file is not required.