AttributeError: module 'lib' has no attribute 'X509_V_FLAG_CB_ISSUER_CHECK'

[guojiubo]

It seems pyOpenSSL needs to be upgrade to >=21.0.0 (to work with cryptography 39.0.1) to fix following issue:

Exception has occurred: AttributeError
module 'lib' has no attribute 'X509_V_FLAG_CB_ISSUER_CHECK'
  File "/Users/guojiubo/Outlook/protool/protool/__init__.py", line 16, in <module>
    import OpenSSL
  File "/Users/guojiubo/Outlook/protool/tests/test_parsing.py", line 9, in <module>
    import protool
AttributeError: module 'lib' has no attribute 'X509_V_FLAG_CB_ISSUER_CHECK'

Associated changes: pyca/pyopenssl#982