Import serialization early to break cyclic import

[tiran]

Fixes: #5794
Signed-off-by: Christian Heimes cheimes@redhat.com

[tiran]

Meh, import cycles from hell!

 ImportError while loading conftest '/home/runner/work/cryptography/cryptography/tests/conftest.py'.
tests/conftest.py:8: in <module>
    from cryptography.hazmat.backends.openssl import backend as openssl_backend
.tox/py39/lib/python3.9/site-packages/cryptography/hazmat/backends/openssl/__init__.py:6: in <module>
    from cryptography.hazmat.backends.openssl.backend import backend
.tox/py39/lib/python3.9/site-packages/cryptography/hazmat/backends/openssl/backend.py:12: in <module>
    from cryptography import utils, x509
.tox/py39/lib/python3.9/site-packages/cryptography/x509/__init__.py:7: in <module>
    from cryptography.x509.base import (
.tox/py39/lib/python3.9/site-packages/cryptography/x509/base.py:12: in <module>
    from cryptography.hazmat._types import _PRIVATE_KEY_TYPES, _PUBLIC_KEY_TYPES
.tox/py39/lib/python3.9/site-packages/cryptography/hazmat/_types.py:7: in <module>
    from cryptography.hazmat.primitives.asymmetric import (
.tox/py39/lib/python3.9/site-packages/cryptography/hazmat/primitives/__init__.py:6: in <module>
    from . import serialization
.tox/py39/lib/python3.9/site-packages/cryptography/hazmat/primitives/serialization/__init__.py:15: in <module>
    from cryptography.hazmat.primitives.serialization.base import (
.tox/py39/lib/python3.9/site-packages/cryptography/hazmat/primitives/serialization/base.py:8: in <module>
    from cryptography.hazmat._types import (
E   ImportError: cannot import name '_PRIVATE_KEY_TYPES' from partially initialized module 'cryptography.hazmat._types' (most likely due to a circular import) (/home/runner/work/cryptography/cryptography/.tox/py39/lib/python3.9/site-packages/cryptography/hazmat/_types.py)
ERROR: InvocationError for command /home/runner/work/cryptography/cryptography/.tox/py39/bin/pytest -n auto --cov=cryptography --cov=tests --capture=no --strict --durations=10 --color=yes --wycheproof-root=wycheproof (exited with code 4)