commit https://github.com/vim/vim/commit/52f9c19015df5ee1ee8592b6f3f15b8a57c8f5be Author: Bram Moolenaar <Bram@vim.org> Date: Sun Mar 13 13:24:45 2016 +0100 patch 7.4.1554 Problem: Completion for :colorscheme does not use 'packpath'. Solution: Make it work, add a test. (Hirohito Higashi)

" Settings for test script execution
" Always use "COMMAND.COM", don't use the value of "$SHELL".
set shell=c:\COMMAND.COM shellquote= shellxquote= shellcmdflag=/c shellredir=>
" This is used only when the +eval feature is available.
if executable("cmd.exe")
   set shell=cmd.exe
endif