old_contents: # Copyright (c) 2006-2016  Andrey Golovizin
  #
  # Permission is hereby granted, free of charge, to any person obtaining
  # a copy of this software and associated documentation files (the
  # "Software"), to deal in the Software without restriction, including
  # without limitation the rights to use, copy, modify, merge, publish,
  # distribute, sublicense, and/or sell copies of the Software, and to
  # permit persons to whom the Software is furnished to do so, subject to
  # the following conditions:
  #
  # The above copyright notice and this permission notice shall be
  # included in all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  # IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  # CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  # TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  # SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  class PybtexError(Exception):
      def __init__(self, message, filename=None):
          super(PybtexError, self).__init__(message)
          self.filename = filename
  
      def get_context(self):
          """Return extra error context info."""
          return None
  
      def get_filename(self):
          """Return filename, if relevant."""
          return self.filename
  
      def __eq__(self, other):
          return unicode(self) == unicode(other)
  
new_contents: # Copyright (c) 2006-2017  Andrey Golovizin
  #
  # Permission is hereby granted, free of charge, to any person obtaining
  # a copy of this software and associated documentation files (the
  # "Software"), to deal in the Software without restriction, including
  # without limitation the rights to use, copy, modify, merge, publish,
  # distribute, sublicense, and/or sell copies of the Software, and to
  # permit persons to whom the Software is furnished to do so, subject to
  # the following conditions:
  #
  # The above copyright notice and this permission notice shall be
  # included in all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  # IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  # CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  # TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  # SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  
  class PybtexError(Exception):
      def __init__(self, message, filename=None):
          super(PybtexError, self).__init__(message)
          self.filename = filename
  
      def get_context(self):
          """Return extra error context info."""
          return None
  
      def get_filename(self):
          """Return filename, if relevant."""
          return self.filename
  
      def __eq__(self, other):
          return unicode(self) == unicode(other)
  
      def __hash__(self):
          return hash(unicode(self))
  
subject: Add PybtexError.__hash__()