patch 8.0.1832: cannot use :unlet for an environment variable commit https://github.com/vim/vim/commit/137374fd6538cf9dee0cb22907728d8fdecb5832 Author: Bram Moolenaar <Bram@vim.org> Date: Sun May 13 15:59:50 2018 +0200 patch 8.0.1832: cannot use :unlet for an environment variable Problem: Cannot use :unlet for an environment variable. Solution: Make it work. Use unsetenv() if available. (Ken Takata, closes #2855)