decode_auth function does not handle utf-8 logins or password

[aebm]

HI

I have found that the function decode_auth (line 96, file) fails when decoding UTF-8 passwords from the .dockercfg file, and load_config returning an empty config.

I have checked and docker hub can handle UTF-8 passwords, this code proves that:

# coding=utf-8
from docker import Client
cred = { 'username': <user>, 'password': <utf-8 password> }
c = Client(base_url='unix://var/run/docker.sock')
res = c.pull(repository='<private container>', tag='latest', auth_config=cred)
print(res)

Thank you