fixed.py

import asyncio

from twisted.internet import asyncioreactor
asyncioreactor.install()

import treq
from twisted.internet.defer import Deferred, ensureDeferred
from twisted.internet.task import react

async def run():
    await treq.get("http://google.com")
    await Deferred.fromFuture(asyncio.ensure_future(asyncio.sleep(1)))

react(lambda x: ensureDeferred(run()))

Here's an idea how to make asyncio Future objects interact with inlineCallbacks automagically:

diff --git a/src/twisted/internet/defer.py b/src/twisted/internet/defer.py
index b14370604..fb2979614 100644
--- a/src/twisted/internet/defer.py
+++ b/src/twisted/internet/defer.py
@@ -1461,6 +1461,10 @@ def _inlineCallbacks(result, g, status):
             status.deferred.errback()
             return

+        if (hasattr(type(result), '_asyncio_future_blocking') and
+                result._asyncio_future_blocking):
+            result = Deferred.fromFuture(result)
+
         if isinstance(result, Deferred):
             # a deferred was yielded, get the result.
             def gotResult(r):

with the above patch, the following code just works:

import asyncio

from twisted.internet import asyncioreactor
asyncioreactor.install()

import treq
from twisted.internet.defer import Deferred, ensureDeferred
from twisted.internet.task import react

async def run():
    print(1)
    await treq.get("http://google.com")
    print(2)
    await asyncio.sleep(1)
    print(3)

react(lambda x: ensureDeferred(run()))

(note that there are no ensure_future() and fromFuture() calls here)