old_contents: ##############################################################################
  # Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
  # Produced at the Lawrence Livermore National Laboratory.
  #
  # This file is part of Spack.
  # Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
  # LLNL-CODE-647188
  #
  # For details, see https://github.com/llnl/spack
  # Please also see the LICENSE file for our notice and the LGPL.
  #
  # This program is free software; you can redistribute it and/or modify
  # it under the terms of the GNU Lesser General Public License (as
  # published by the Free Software Foundation) version 2.1, February 1999.
  #
  # This program 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 terms and
  # conditions of the GNU Lesser General Public License for more details.
  #
  # You should have received a copy of the GNU Lesser General Public
  # License along with this program; if not, write to the Free Software
  # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  ##############################################################################
  from spack import *
  
  
  class Bison(AutotoolsPackage):
      """Bison is a general-purpose parser generator that converts
      an annotated context-free grammar into a deterministic LR or
      generalized LR (GLR) parser employing LALR(1) parser tables."""
  
      homepage = "http://www.gnu.org/software/bison/"
      url      = "http://ftp.gnu.org/gnu/bison/bison-3.0.tar.gz"
  
      version('3.0.4', 'a586e11cd4aff49c3ff6d3b6a4c9ccf8')
  
      depends_on('m4', type=('build', 'run'))
  
      patch('pgi.patch', when='@3.0.4')
  
      build_directory = 'spack-build'
  
new_contents: ##############################################################################
  # Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
  # Produced at the Lawrence Livermore National Laboratory.
  #
  # This file is part of Spack.
  # Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
  # LLNL-CODE-647188
  #
  # For details, see https://github.com/llnl/spack
  # Please also see the LICENSE file for our notice and the LGPL.
  #
  # This program is free software; you can redistribute it and/or modify
  # it under the terms of the GNU Lesser General Public License (as
  # published by the Free Software Foundation) version 2.1, February 1999.
  #
  # This program 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 terms and
  # conditions of the GNU Lesser General Public License for more details.
  #
  # You should have received a copy of the GNU Lesser General Public
  # License along with this program; if not, write to the Free Software
  # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  ##############################################################################
  from spack import *
  
  
  class Bison(AutotoolsPackage):
      """Bison is a general-purpose parser generator that converts
      an annotated context-free grammar into a deterministic LR or
      generalized LR (GLR) parser employing LALR(1) parser tables."""
  
      homepage = "http://www.gnu.org/software/bison/"
      url      = "http://ftp.gnu.org/gnu/bison/bison-3.0.tar.gz"
  
      version('3.0.4', 'a586e11cd4aff49c3ff6d3b6a4c9ccf8')
      version('2.7',   'ded660799e76fb1667d594de1f7a0da9')
  
      depends_on('m4', type=('build', 'run'))
  
      patch('pgi.patch', when='@3.0.4')
  
      build_directory = 'spack-build'
  
subject: add older bison version 2.7 (#3645)