docs: def compile_dir(dfn, optimize_python=True):
      '''
      Compile *.py in directory `dfn` to *.pyo
      '''
  
      if PYTHON is None:
          return
  
      if int(PYTHON_VERSION[0]) >= 3:
          args = [PYTHON, '-m', 'compileall', '-b', '-f', dfn]
      else:
          args = [PYTHON, '-m', 'compileall', '-f', dfn]
      if optimize_python:
          # -OO = strip docstrings
          args.insert(1, '-OO')
      return_code = subprocess.call(args)
  
      if return_code != 0:
          print('Error while running "{}"'.format(' '.join(args)))
          print('This probably means one of your Python files has a syntax '
                'error, see logs above')
          exit(1)