I think this is because you don't have the gdata module for Python installed. I have rewritten parts of the workflow to pull the JSON feed from Google directly and not use the gdata module. Instead, the urllib and json modules are used and I bet you have these installed
Could you try to download the workflow again from this link and reinstall it? Maybe you have to delete the previous and install the new. I don't know if Alfred will overwrite previous installations of a workflow. Please let me hear if it works