Vim - create balloon message text out of lint messages

createLintBalloonText.vim

function! LintBalloon()
   let BalloonText_l = [] 
   " read lint output into a list
   let LintOutput_l=readfile("project.lnt")
   " iterate through list
   for line in LintOutput_l
      " find the message lines and capture the pure message (here for standard gcc format)
      let Match_l = matchlist(line, '^' . expand('%:.') . ':' . v:beval_lnum .':\d\+: \(.*\)')
      if len(Match_l) != 0 " if match
          " add all matching lines to list
          call add(BalloonText_l, Match_l[1])
      endif
   endfor
   return join(BalloonText_l, "\n\n")
endfunction