EL9 rejects sha1 signatures by default

[DrDaveD]

On a default-configured EL9 the internal tests fail because sha1 signatures are rejected for certificates. A workaround is to change the configuration with

sudo update-crypto-policies --set DEFAULT:SHA1

I attempted a fix for this in #30 by converting from M2crypto to cryptography packages, but gave up on that. Perhaps there's a workaround by clever use of M2crypto functions, but so far I haven't found it.