old_contents: from __future__ import division
  
  try:
    import i19.util.version as version
    print version.i19_version()
  except ImportError:
    pass
  
new_contents: from __future__ import division
  
  try:
    import i19.util.version as version
    print version.i19_version()
  except ImportError:
    pass
  
  try:
    import libtbx.pkg_utils
    libtbx.pkg_utils.require('mock', '>=2.0')
    libtbx.pkg_utils.require('pytest', '>=2')
  except ImportError:
    print "\n" * 10 + "Could not verify dependencies: cctbx sources out of date" + "\n" * 10
  
subject: define dependencies