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
  
  # Define this first, since it is referenced by _re2.
  class error(Exception):
      pass
  
  import _re2
  
  compile = _re2._compile
  
subject: Use PEP-8-compliant 4-space indent in re2.py