old_contents: #!/usr/bin/env python3
  from setuptools import setup
  
  
  def requirements(section=None):
      """Helper for loading dependencies from requirements files."""
      if section is None:
          filename = "requirements.txt"
      else:
          filename = f"requirements-{section}.txt"
  
      with open(filename) as file:
          return [line.strip() for line in file]
  
  
  # See setup.cfg for the actual configuration.
  setup(
      # setup needs to be able to import the library, for attr: to work
      setup_requires=['pytest-runner'],
      tests_require=requirements('tests'),
  )
  
new_contents: #!/usr/bin/env python3
  from setuptools import setup
  
  
  def requirements(section=None):
      """Helper for loading dependencies from requirements files."""
      if section is None:
          filename = "requirements.txt"
      else:
          filename = f"requirements-{section}.txt"
  
      with open(filename) as file:
          return [line.strip() for line in file]
  
  
  # See setup.cfg for the actual configuration.
  setup(
      setup_requires=['pytest-runner'],
      tests_require=requirements('tests'),
  )
  
subject: Drop obsolete comment