Can't create auto-save files when using tramp on Windows

[Park Hays]

I have seen several comments about auto-save in emacs on Windows for TRAMP.

The symptoms are described here:
http://emacs.1067599.n8.nabble.com/Can-t-create-auto-save-files-when-using-tramp-on-Windows-td412612.html

I have a likely diagnosis based on my system's behavior.

Local: emacs 25.1 (via Vincent Goulet)

Tramp with plink

Remote: redhat derivative

Typical error (username, filenames are substituted)
Auto-saving codefile.py: Opening output file: Invalid argument, c:/Users/Me/AppData/Local/Temp/#!plink:RemoteHost:!home!Me!RemoteDir!codefile.py#

The "invalid argument" aspects are almost certainly caused by the colon character after plink. Windows file name characters do not allow a colon (:) to be used. See this StackExchange discussion:

http://stackoverflow.com/questions/1976007/what-characters-are-forbidden-in-windows-and-linux-directory-names

I had initially thought the uniquify argument could be made a hashing or safe conversion method, but it appears that I would have to override things deep in TRAMP, and that others might be having this problem as well.

My short term workaround is to turn off auto-save in TRAMP buffers with
(add-to-list 'backup-directory-alist
             (cons tramp-file-name-regexp nil))