I wasn't able to get this working, but these changes helped me progress.

[MaxPleaner]

removing --use-mirrors made pip install work for me.

the heroku create command threw an error unless the --stack-cedar flag was replaced by -s cedar

I'm on Linux Mint (Ubuntu) using the latest heroku toolbelt.

heroku-toolbelt/3.42.21 (x86_64-linux) ruby/2.2.3