old_contents: #!/usr/bin/env python
  
  import os, stat, urllib2
  
  f = urllib2.urlopen('http://waf.googlecode.com/files/waf-1.7.11')
  
  with open('waf', 'wb') as waf:
      waf.write(f.read())
  
  os.chmod('waf', os.stat('waf').st_mode | stat.S_IXUSR)
  
new_contents: #!/usr/bin/env python
  
  import os, stat, urllib.request
  
  urllib.request.urlretrieve('https://waf.googlecode.com/files/waf-1.7.11', 'waf')
  os.chmod('waf', os.stat('waf').st_mode | stat.S_IXUSR)
  
subject: Update bootstrap script to Python 3.