I have been using _msvcompiler.py from Python 3.5 to build some executables but I have been unable to get it to generate and embed a  manifest.  

When I looked into this I found that the subroutine that sets up the parameters for generating a manifest ('manifest_get_embed_info'  at around line 471) has the line:

        ld_args.append('/MANIFESTFILE:' + temp_manifest)

to set the manifest's name but doesn't actually ask for a manifest to be generated.  Here is what is said about /MANIFESTFILE on MSDN:

"/MANIFESTFILE will have no effect if you do not also link with /MANIFEST."

After adding:

        ld_args.append('/MANIFEST')

before the above line, I then succeed in obtaining the manifest.