Note that using "whatever version of python the name 'python' maps to in the current shell environment" is more error-prone that specifying which python you mean, such as by executing "/usr/bin/python setup.py" instead of executing "./setup.py". When you build tahoe (by running "make") it will make a copy of bin/allmydata-tahoe in instdir/bin/allmydata-tahoe with the shebang line rewritten to execute the specific version of python that was used when building instead of to execute "/usr/bin/env python".
However, it seems better that the default for lazy people be "whatever 'python' means currently" instead of "whatever 'python' meant to the manufacturer of your operating system".
from allmydata.scripts import runner
runner.run()
from allmydata.scripts import runner
runner.run()
from foolscap import Tub
from foolscap.eventual import eventually
from foolscap import Tub
from foolscap.eventual import eventually
from distutils.core import setup
from distutils.core import Extension
from distutils.core import setup
from distutils.core import Extension
import sha as shamodule
import os, random
import sha as shamodule
import os, random
import random, math, os, re
from twisted.python import usage
import random, math, os, re
from twisted.python import usage
import os, sys, signal, time
from twisted.python import usage
import os, sys, signal, time
from twisted.python import usage
from twisted.trial import unittest
from twisted.internet import defer
from twisted.trial import unittest
from twisted.internet import defer
from zope.interface import implements
from twisted.trial.itrial import IReporter
from zope.interface import implements
from twisted.trial.itrial import IReporter