For instance, if \":\" is invalid as a file character in file names
on your system, you could say something like:
-\(setq nnheader-file-name-translation-alist '((?: . ?_)))")
+\(setq nnheader-file-name-translation-alist \\='((?: . ?_)))")
(defvar nnheader-directory-separator-character
(string-to-char (substring (file-name-as-directory ".") -1))