bootstrap.py file is updated from time to time from:
  http://svn.zope.org/*checkout*/zc.buildout/trunk/bootstrap/bootstrap.py
or:
  http://svn.zope.org/*checkout*/zc.buildout/tags/RELEASE/bootstrap/bootstrap.py

There is no need to fix it locally, all changes shall go upstream.
Moreover buildout has ability to autoupdate itself, so local manipulations on
that file might have side effects.