Update python-gnupg and relax constraint

[sevein]

We were some versions behind, in particular v0.4.4 addresses CVE-2019-6690.

It needs to be tested.

Connects to archivematica/Issues#1317.

[replaceafill]

I tested this and found an issue when I run the aip-encrypt and aip-encrypt-mirror tags of the acceptance tests where the GPG space is never created. I also noticed the /administration/keys/ view raises ValueError: gnupghome should be a directory (it isn't): /var/archivematica/storage_service/.gnupg which doesn't seem familiar:

I couldn't find anything in the AM or SS code that creates that directory, and then I looked at the python-gnupg changelog which lead me to a related change in 0.4.5 where the .gnupg directory is not created anymore. Someone reported a similar problem and the author answered with:

With this change, the caller is responsible for ensuring that the directory exists beforehand.

[replaceafill]

Thanks!