old_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  
  from metrika.engine import Engine
  import glob
  
  __author__ = 'Javier Pimás'
  
  
  if __name__ == '__main__':
  
      engine = Engine()
  
      modules = []
      for module_name in glob.glob("measure_*.py"):
          modules.append(__import__(module_name[:-3]))
  
      for module in modules:
          module.configure(engine)
  
      engine.go()
  
  # example of how to run:
  # $> python -m metrika run join-speed test
  
new_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  import sys
  if sys.version_info < (3, 4):
      raise Exception("must use python 3.4 or greater")
  
  from metrika.engine import Engine
  import glob
  __author__ = 'Javier Pimás'
  
  
  
  if __name__ == '__main__':
  
      engine = Engine()
  
      modules = []
      for module_name in glob.glob("measure_*.py"):
          modules.append(__import__(module_name[:-3]))
  
      for module in modules:
          module.configure(engine)
  
      engine.go()
  
  # example of how to run:
  # $> python -m metrika run join-speed test
  
subject: throw error when trying to run in old pythons