Use of PyPyModule_FromDefAndSpec2 is broken with pypy 7.3.19

The package cryptography-50.0.0-pp311-pypy311_pp73-manylinux_2_34_x86_64.whl, which uses PyO3, is incompatible with the PyPy interpreter in Debian 13.

$ virtualenv -ppypy3 /tmp/aa
[...]
$ /tmp/aa/bin/pip install cryptography==50.0.0
Collecting cryptography==50.0.0
  Using cached cryptography-50.0.0-pp311-pypy311_pp73-manylinux_2_34_x86_64.whl.metadata (4.3 kB)
Using cached cryptography-50.0.0-pp311-pypy311_pp73-manylinux_2_34_x86_64.whl (4.7 MB)
Installing collected packages: cryptography
Successfully installed cryptography-50.0.0
 
[notice] A new release of pip is available: 25.1.1 -> 26.2.1
[notice] To update, run: /tmp/aa/bin/pypy3 -m pip install --upgrade pip
$ /tmp/aa/bin/python
Python 3.11.11 (7.3.19+dfsg-2, Apr 11 2025, 02:57:20)
[PyPy 7.3.19 with GCC 14.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>> import cryptography.x509
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/tmp/aa/lib/pypy3.11/site-packages/cryptography/x509/__init__.py", line 7, in <module>
    from cryptography.x509 import certificate_transparency, oid, verification
  File "/tmp/aa/lib/pypy3.11/site-packages/cryptography/x509/certificate_transparency.py", line 8, in <module>
    from cryptography.hazmat.bindings._rust import x509 as rust_x509
ImportError: /tmp/aa/lib/pypy3.11/site-packages/cryptography/hazmat/bindings/_rust.pypy311-pp73-x86_64-linux-gnu.so: undefined symbol: PyPyModule_FromDefAndSpec2

The PyModule_FromDefAndSpec2 function was apparently added to PyPy in version 7.3.20. PyO3 claims to support "PyPy 7.3 (Python 3.11+)", as the "pypy311_pp73" tag implies.

The use of this function in PyO3 appears to have been added in version 0.27.0. Accordingly, cryptography version 47.0.0 (pyo3 version 0.28.3) and later appear to be broken, while cryptography version 46.0.7 (pyo3 version 0.26.0) and earlier do not have this issue.

Start by tracing the PyO3 0.27.0 change that introduced PyPyModule_FromDefAndSpec2 and compare its assumptions with PyPy 7.3.19 and 7.3.20. Done means the generated PyPy extension no longer references an unavailable symbol on PyPy 7.3.19 while retaining compatibility with supported newer versions.