It appears Microsoft has removed some of the prerequisite files from the web servers that the installation calls for downloads.

The links provided for the prerequisites for download and installation in the Setup.exe (CU 6) are broken and this causes the installation to fail.  Found this out by using a power shell script to create a redistributable pack.

Files that are returning a 404 not found error:
      Microsoft Sign-in Assistant
      Windows Identity Foundation

Solution would be to put the files requested by the setup back on the Microsoft web server.  Do you know if they are working of fixing this?