PubSub emulator: read config from JSON environment variable

[ollosh]

Since there were some talks about the push endpoints and the fast implementation was a bit clumsy, I've added the support for the pubsub emulator to be automatically configured from JSON config.

Temporary image: ollosh/gcloud-pubsub-emulator

Added

• Support for JSON config via environment variable

[ollosh]

Not really a python expert so not sure what is the best way to handle this static analysis issue. If anyone can lend a hand, I'd be grateful :bow:

[ollosh]

@TheKevJames bumping this, maybe you see this useful

[TheKevJames]

@ollosh sorry for taking so long on this one! I really do appreciate the PR :)

I've decided to go with a file-based configuration, please see #727. I'll be getting it merged and included in the next release right away!

[ollosh]

@TheKevJames No problem, that's why I was using my image temporarily :) Also, having used my approach with an env variable for a while, it is a bit cumbersome when you're modifying the configuration so it does make sense to go with the config file.