Managing proxied gateways

Simple proxying

Using the via arg of specs we can create a gateway whose io is created on a remote gateway and proxied to the master.

The simplest use case, is where one creates one master process and uses it to control new workers and their environment

>>> import execnet
>>> group = execnet.Group()
>>> group.defaultspec = 'popen//via=master'
>>> master = group.makegateway('popen//id=master')
>>> master
<Gateway id='master' receive-live, thread model, 0 active channels>
>>> worker = group.makegateway()
>>> worker
<Gateway id='gw0' receive-live, thread model, 0 active channels>
>>> group
<Group ['master', 'gw0']>