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Hi all!

Currently _spawn_worker in the conductor manager raises 
NoFreeConductorWorker if pool is already full. That's not very user 
friendly (potential source of retries in client) and does not map well 
on common async worker patterns.

My understanding is that it was done to prevent the conductor thread 
from waiting on pool to become free. If this is true, we no longer need 
it after switch to Futurist, as Futurist maintains internal queue for 
its green executor, just like thread and process executors in stdlib do. 
Instead of blocking the conductor the request will be queued, and a user 
won't have to retry vague (and rare!) HTTP 503 error.

WDYT about me dropping this exception with move to Futurist?

Dmitry