Customizing flymake output

gistfile1.el

(defadvice flymake-post-syntax-check (before coffee-no-spaces activate)
  "Warn about space indentation when in coffee-mode."
  (when (eq major-mode 'coffee-mode)
    (let (bad-spaces)
      (save-excursion
        (goto-char (point-min))
        (while (re-search-forward
                "^[[:blank:]]*\\(?1: \\)[[:blank:]]*[^[:blank:]\n]"
                nil t)
          (let (( ppss (syntax-ppss (match-beginning 1))))
            (unless (or (nth 4 ppss) (nth 3 ppss))
              (push (match-beginning 1) bad-spaces)))))
      (mapc (lambda (space)
              (let* (( linum (line-number-at-pos space))
                     ( ler (flymake-ler-make-ler
                            buffer-file-name
                            linum
                            "w"
                            "Line contains space indentation.")))
                (if (assoc linum flymake-new-err-info)
                    (push ler (cadr (assoc linum flymake-new-err-info)))
                  (push (list linum (list ler)) flymake-new-err-info))))
            bad-spaces)
      (setq flymake-new-err-info
            (sort flymake-new-err-info
                  (lambda (a b) (< (car a) (car b)))))
      )))