Remove asyncio metaprogramming

To transparently support both synchronous and asynchronous usage we use metaprogrmming. Basically, our mixin matches method calls to the context type we run within.

When a synchronous controller is used within an event handler we mistakenly treat it as being asynchronous. For example...

from stem.control import Controller, EventType

with Controller.from_port() as controller:
  controller.authenticate()
  print(controller.get_version())  # this prints our version

  def listener_func(event):
   print(controller.get_version())  # this prints "<coroutine object Controller.get_version at 0x7f87d29da640>"

  controller.add_event_listener(listener_func, EventType.BW)

  input()

The trouble here is that our listener invokes within our controller, which is an asynchronous context. Needless to say, this is confusing as hell.

I'm going to revisit and likely remove our asyncio metaprogramming. It's complicated, breaks type checks, and liable to keep causing problems. Pitching this on the python list and stack overflow I get the sense that this isn't a promising approach long term.

torproject / stem

Remove asyncio metaprogramming #77