old_contents: #! /usr/bin/env python
  
  from setuptools import setup
  
  
  PACKAGENAME = 'preconditions'
  
  
  setup(
      name=PACKAGENAME,
      description='Flexible, concise preconditions.',
      url='https://github.com/nejucomo/{0}'.format(PACKAGENAME),
      license='MIT',
      version='0.1.dev0',
      author='Nathan Wilcox',
      author_email='nejucomo@gmail.com',
      py_modules=[PACKAGENAME],
      test_suite='tests',
      )
  
new_contents: #! /usr/bin/env python
  
  import sys
  from setuptools import setup
  
  if 'upload' in sys.argv:
      if '--sign' not in sys.argv and sys.argv[1:] != ['upload', '--help']:
          raise SystemExit('Refusing to upload unsigned packages.')
  
  
  PACKAGENAME = 'preconditions'
  
  
  setup(
      name=PACKAGENAME,
      description='Flexible, concise preconditions.',
      url='https://github.com/nejucomo/{0}'.format(PACKAGENAME),
      license='MIT',
      version='0.1.dev0',
      author='Nathan Wilcox',
      author_email='nejucomo@gmail.com',
      py_modules=[PACKAGENAME],
      test_suite='tests',
      )
  
subject: Add a "signature requirement" to the sdist upload command.