asyncio: Drop support for trollius

This package is no longer maintained and was never widely used.

.travis.yml

@@ -18,7 +18,7 @@ python:
     - pypy3.5-5.7.1-beta
 
 install:
-    - if [[ $TRAVIS_PYTHON_VERSION == 2* ]]; then travis_retry pip install futures mock monotonic trollius; fi
+    - if [[ $TRAVIS_PYTHON_VERSION == 2* ]]; then travis_retry pip install futures mock monotonic; fi
     - if [[ $TRAVIS_PYTHON_VERSION == 'pypy' ]]; then travis_retry pip install futures mock; fi
     # TODO(bdarnell): pycares tests are currently disabled on travis due to ipv6 issues.
     #- if [[ $TRAVIS_PYTHON_VERSION != 'pypy'* ]]; then travis_retry pip install pycares; fi
@@ -67,7 +67,6 @@ script:
     - if [[ $TRAVIS_PYTHON_VERSION != pypy* ]]; then python $TARGET --resolver=tornado.netutil.ThreadedResolver; fi
     - if [[ $TRAVIS_PYTHON_VERSION == 2* ]]; then python $TARGET --httpclient=tornado.curl_httpclient.CurlAsyncHTTPClient; fi
     - if [[ $TRAVIS_PYTHON_VERSION == 2* ]]; then python $TARGET --ioloop=tornado.platform.twisted.TwistedIOLoop; fi
-    - if [[ $TRAVIS_PYTHON_VERSION == 2* ]]; then python $TARGET --ioloop=tornado.platform.asyncio.AsyncIOLoop; fi
     - if [[ $TRAVIS_PYTHON_VERSION == 2* ]]; then python $TARGET --resolver=tornado.platform.twisted.TwistedResolver; fi
     - if [[ $TRAVIS_PYTHON_VERSION == 2* ]]; then python $TARGET --ioloop=tornado.ioloop.PollIOLoop --ioloop_time_monotonic; fi
     #- if [[ $TRAVIS_PYTHON_VERSION != pypy* ]]; then python $TARGET --resolver=tornado.platform.caresresolver.CaresResolver; fi

tornado/platform/asyncio.py

@@ -26,17 +26,7 @@ from tornado.gen import convert_yielded
 from tornado.ioloop import IOLoop
 from tornado import stack_context
 
-try:
-    # Import the real asyncio module for py33+ first.  Older versions of the
-    # trollius backport also use this name.
-    import asyncio  # type: ignore
-except ImportError as e:
-    # Asyncio itself isn't available; see if trollius is (backport to py26+).
-    try:
-        import trollius as asyncio  # type: ignore
-    except ImportError:
-        # Re-raise the original asyncio error, not the trollius one.
-        raise e
+import asyncio
 
 
 class BaseAsyncIOLoop(IOLoop):

tox.ini

@@ -30,7 +30,6 @@ envlist =
         py2-select,
         py2-full-twisted,
         py2-twistedlayered,
-        py2-full-trollius,
 
         # Alternate Resolvers.
         {py2,py3}-full-{threadedresolver},
@@ -80,7 +79,6 @@ deps =
      {py2,py27,pypy,pypy3}-full: mock
      # singledispatch became standard in py34.
      {py2,py27,pypy}-full: singledispatch
-     trollius: trollius
      py2-monotonic: monotonic
      sphinx: sphinx
      sphinx: sphinx_rtd_theme
@@ -119,7 +117,6 @@ commands =
          select: --ioloop=tornado.platform.select.SelectIOLoop \
          twisted: --ioloop=tornado.platform.twisted.TwistedIOLoop \
          twistedlayered: --ioloop=tornado.test.twisted_test.LayeredTwistedIOLoop --resolver=tornado.platform.twisted.TwistedResolver \
-         trollius: --ioloop=tornado.platform.asyncio.AsyncIOLoop \
          caresresolver: --resolver=tornado.platform.caresresolver.CaresResolver \
          threadedresolver: --resolver=tornado.netutil.ThreadedResolver \
          monotonic: --ioloop=tornado.ioloop.PollIOLoop --ioloop_time_monotonic \