bug#31079: Windows - Emacs-25.3.1 Can't find source.tex file

[gojjoe]

PS:

> My value is
> 
> .;c:/Users/[omitted]/.emacs.d/elpa/auctex-12.1.1/latex;C:/Users/[omitted]/texmf/tex/;

Curiously, only the last directory appears in my environment variable if I call 
it from a command prompt, outside Emacs. So the first two directories seem to 
be provided by AUCTeX itself.

I'm curious to see what its value is for you when called from Emacs in the way 
I described. You could also try the same with the old, working auctex version, 
to see if you get different results.

Cheers,
J