Having Python 2.7, Python 3.6 and Python 3.7 on your Mac OS X at the same time turns your environment into a mess, when you try to use CLI tools distributed as PIP packages.
Digging into logs can take hours with no luck. I see here few guides about installing AWS CLI, but sadly none of them worked for me. If you reading this, I probably suggest you an obvious thing: just follow instruction on official doc @ docs.aws.amazon.com:
curl "https://d1vvhvl2y92vvt.cloudfront.net/awscli-exe-macos.zip" -o "awscliv2.zip" unzip awscliv2.zip sudo ./aws/install
aws2 configure and you are ready to go ahead.