new_contents: #!/usr/bin/python
  import sys
  from datetime import datetime
  
  if __name__ == "__main__":
      newversion = sys.argv[1]
  
      with open("CHANGELOG.rst", "r") as fl:
          lines = fl.readlines()
  
      for i, line in enumerate(lines):
          if line == "dev-version\n":
              break
      else:
          raise IOError("Couldn't Find 'dev-version' tag")
  
      lines.insert(i + 2, "----------------------\n")
      lines.insert(i + 2, f'v{newversion} [{datetime.now().strftime("%d %b %Y")}]\n')
      lines.insert(i + 2, "\n")
  
      with open("CHANGELOG.rst", "w") as fl:
          fl.writelines(lines)
  
subject: add changethelog