commit https://github.com/vim/vim/commit/169ebb080454357279ad5ad21ac532deaec605e8 Author: Bram Moolenaar <Bram@vim.org> Date: Wed Sep 7 23:32:23 2016 +0200 patch 7.4.2344 Problem: The "Reading from channel output..." message can be unwanted. Appending to a buffer leaves an empty first line behind. Solution: Add the "out_msg" and "err_msg" options. Writing the first line overwrites the first, empty line.

" Vim compiler file
" Compiler:	Unit testing tool for Python
" Maintainer:	Max Ischenko <mfi@ukr.net>
" Last Change: 2004 Mar 27

if exists("current_compiler")
  finish
endif
let current_compiler = "pyunit"

if exists(":CompilerSet") != 2		" older Vim always used :setlocal
  command -nargs=* CompilerSet setlocal <args>
endif

CompilerSet efm=%C\ %.%#,%A\ \ File\ \"%f\"\\,\ line\ %l%.%#,%Z%[%^\ ]%\\@=%m