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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def download_and_bootstrap(src, name, prereq=None):
 """ Download and install something if 'prerequisite' fails """

    if prereq:
        prereq_cmd = '{0} -c "{1}"'.format(PY_EXE, prereq)
        rv = os.system(prereq_cmd)
        if rv == 0:
            return

    ulp = urllib2.urlopen(src)
    fp = open(name, "wb")
    fp.write(ulp.read())
    fp.close()
    cmdline = "{0} {1}".format(PY_EXE, name)
    rv = os.system(cmdline)
    assert rv == 0