BentoML

I’m now wondering since i found the extra index url in `requirements.txt` whether those pip install arguments can’t all just be put into `/etc/pip.conf` so that all pip invocations can use it

<@U01BNKWNTMM> I think we probably should also pass the `extra_args` for installing the `bundled_pip_dependencies`

I am not sure to have all of the arguments in `/etc/pip.conf` thou.  Feel like that could cause additional headaches, if the conf is not available on the image build machine, and one extra thing users have to be aware of

thanks for the input <@UKH494PHP>. i created a github issue <https://github.com/bentoml/BentoML/issues/1296>