Thanks, it's very helpful to see the exact error message!
It looks like several people have had the same problem:
https://community.letsencrypt.org/search?q=ensurepip
One person claimed to solve it by setting the locale:
I don't immediately understand why that would be relevant here, but maybe you could try that and report back on whether it works? If it doesn't, we can try to get some other people involved with more knowledge of the dependencies and packaging issues.