old_contents: #!/usr/bin/env python
  
  # Define this first, since it is referenced by _re2.
  class error(Exception):
      pass
  
  import _re2
  
  compile = _re2._compile
  
new_contents: #!/usr/bin/env python
  
  # Copyright (c) 2010, David Reiss and Facebook, Inc. All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  # * Redistributions of source code must retain the above copyright
  #   notice, this list of conditions and the following disclaimer.
  # * Redistributions in binary form must reproduce the above copyright
  #   notice, this list of conditions and the following disclaimer in the
  #   documentation and/or other materials provided with the distribution.
  # * Neither the name of Facebook nor the names of its contributors
  #   may be used to endorse or promote products derived from this software
  #   without specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  # PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  # HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  # Define this first, since it is referenced by _re2.
  class error(Exception):
      pass
  
  import _re2
  
  compile = _re2._compile
  
subject: Add a copyright and license comment to re2.py