Refactor how net/data/verify_certificate_chain_unittest/*

net/data/verify_certificate_chain_unittest/generate-basic-constraints-pathlen-0-self-issued.py

-#!/usr/bin/python
-# Copyright (c) 2015 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-"""Certificate chain with 2 intermediates. The first intermediate has a basic
-constraints path length of 0. The second one is self-issued so does not count
-against the path length."""
-
-import common
-
-# Self-signed root certificate (used as trust anchor).
-root = common.create_self_signed_root_certificate('Root')
-
-# Intermediate with pathlen 0
-intermediate1 = common.create_intermediate_certificate('Intermediate', root)
-intermediate1.get_extensions().set_property('basicConstraints',
-                                            'critical,CA:true,pathlen:0')
-
-# Another intermediate (with the same pathlen restriction).
-# Note that this is self-issued but NOT self-signed.
-intermediate2 = common.create_intermediate_certificate('Intermediate',
-                                                       intermediate1)
-intermediate2.get_extensions().set_property('basicConstraints',
-                                            'critical,CA:true,pathlen:0')
-
-# Target certificate.
-target = common.create_end_entity_certificate('Target', intermediate2)
-
-chain = [target, intermediate2, intermediate1]
-trusted = common.TrustAnchor(root, constrained=False)
-time = common.DEFAULT_TIME
-key_purpose = common.DEFAULT_KEY_PURPOSE
-verify_result = True
-errors = None
-
-common.write_test_file(__doc__, chain, trusted, time, key_purpose,
-                       verify_result, errors)