Hello,
using ipv6 http/s proxy seems to not work.

Test with http(s)_proxy on localhost ipv4 : aws cli is working
Test with http(s)_proxy with ipv6 adddress : export https_proxy="http://[xxxx:xxxx:xxxx]:8080" does not work.
(Caused by ProxyError('Cannot connect to proxy.', gaierror(-2, 'Name or service not known')))

[WSO-ROSAPARKS-3b714fa2-f497-ce7d-eb15-b8aeedea2f3c]aws --version
aws-cli/1.12.2 Python/2.7.9 Linux/4.9.23 botocore/1.8.2

Regards,
Nicolas Prochazka