To fix this failure on the CI tests:
```
File "/__w/ckanext-harvest/ckanext-harvest/ckanext/harvest/harvesters/ckanharvester.py", line 7, in <module>
from urllib3.contrib import pyopenssl
File "/usr/lib/python3.9/site-packages/urllib3/contrib/pyopenssl.py", line 50, in <module>
import OpenSSL.SSL
File "/usr/lib/python3.9/site-packages/OpenSSL/__init__.py", line 8, in <module>
from OpenSSL import crypto, SSL
File "/usr/lib/python3.9/site-packages/OpenSSL/crypto.py", line 1550, in <module>
class X509StoreFlags(object):
File "/usr/lib/python3.9/site-packages/OpenSSL/crypto.py", line 1570, in X509StoreFlags
CB_ISSUER_CHECK = _lib.X509_V_FLAG_CB_ISSUER_CHECK
AttributeError: module 'lib' has no attribute 'X509_V_FLAG_CB_ISSUER_CHECK'
```