Allow local variables section to begin with a square bracket

Fixes Bug#27391.

* lisp/international/mule.el (find-auto-coding): Fix regular
expression for "Local Variables" section.

* test/lisp/international/mule-tests.el (find-auto-coding--bug27391):
Add unit test.

lisp/international/mule.el

@@ -1970,7 +1970,7 @@ use \"coding: 'raw-text\" instead."
 	  (goto-char tail-start)
 	  (re-search-forward "[\r\n]\^L" tail-end t)
 	  (if (re-search-forward
-	       "[\r\n]\\([^[\r\n]*\\)[ \t]*Local Variables:[ \t]*\\([^\r\n]*\\)[\r\n]"
+	       "[\r\n]\\([^\r\n]*\\)[ \t]*Local Variables:[ \t]*\\([^\r\n]*\\)[\r\n]"
 	       tail-end t)
 	      ;; The prefix is what comes before "local variables:" in its
 	      ;; line.  The suffix is what comes after "local variables:"

test/lisp/international/mule-tests.el

@@ -0,0 +1,39 @@
+;;; mule-tests.el --- unit tests for mule.el         -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2017 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for lisp/international/mule.el.
+
+;;; Code:
+
+(ert-deftest find-auto-coding--bug27391 ()
+  "Check that Bug#27391 is fixed."
+  (with-temp-buffer
+    (insert "\n[comment]: # ( Local Variables: )\n"
+            "[comment]: # ( coding: utf-8	)\n"
+            "[comment]: # ( End:		)\n")
+    (goto-char (point-min))
+    (should (equal (let ((auto-coding-alist ())
+                         (auto-coding-regexp-alist ())
+                         (auto-coding-functions ()))
+                     (find-auto-coding "" (buffer-size)))
+                   '(utf-8 . :coding)))))
+
+;;; mule-tests.el ends here