Steps to reproduce:
1. Create empty project
2. Go to "Build settings..."
3. Select Windows Store platform
4. Press "Open Download page"
-- Notice error in the browser which says that UnitySetup-Metro-Support-for-Editor-5.4.0b##.pkg was not found on this server. Similar 404 error with 5.3 versions.

Reproduced with: 5.4.0b17; 5.4.0b07; 5.3.4f1; 5.3.4p6

Note: Reproducible only with OS X. You cannot use Windows Store module on OSX, because Visual Studio and Windows SDK are required, and those cannot be installed on OSX.