Fix DeprecationError when ussing assert_ since python 3.12

[mirespace]

Dear Maintainer,

In Ubuntu we cannot build this package (FTBFS): since python3.12, the assert_ method no longer exists [1]. We could see a deprecation warning for this in previous builds, like this one for Focal [2]:

test_object_hook (tests.PhpSerializeTestCase) ... /<>/tests.py:92: DeprecationWarning: Please use assertTrue instead.
self.assert_(b'WP_User' in x)

In Debian, they still use Python3.11 (so they have the warning, not the error like us) [3].

I'm submitting here the change that we have already incorporated into the Ubuntu package for your awareness in case you find it useful.

Thanks in advance!

[1] https://docs.python.org/3/library/unittest.html#assert-methods
[2] https://launchpadlibrarian.net/448504127/buildlog_ubuntu-focal-amd64.python-phpserialize_1.3-1.1_BUILDING.txt.gz
[3] https://buildd.debian.org/status/fetch.php?pkg=python-phpserialize&arch=all&ver=1.3-2&stamp=1712878490&raw=0

[jgarte]

Hi,

I also get this:

Traceback (most recent call last):
  File "/tmp/guix-build-python-phpserialize-1.3.drv-0/source/tests.py", line 35, in test_dumps_dict
    self.assertEqual(phpserialize.dumps({'a': 1, 'b': 2, 'c': 3}),
AssertionError: b'a:3:{s:1:"a";i:1;s:1:"b";i:2;s:1:"c";i:3;}' != b'a:3:{s:1:"a";i:1;s:1:"c";i:3;s:1:"b";i:2;}'

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