'Makes a zip file archive containing len(contents) files.  Contents
should be a list of strings, each string being the content of one file.'

def makeZipFile(self, contents, directory=''):

    zpfilename = self.testdir.child('zipfile.zip').path
    with zipfile.ZipFile(zpfilename, 'w') as zpfile:
        for (i, content) in enumerate(contents):
            filename = str(i)
            if directory:
                filename = ((directory + '/') + filename)
            zpfile.writestr(filename, content)
    return zpfilename
