On python3.4+, only support asyncio and expose it to rplugins

Dissallow python3.3
python2.7 is unchanged (pyuv is still preferred; loop not exposed)

.travis.yml

@@ -16,7 +16,6 @@ python:
   # If the build matrix gets bigger, also update the number of runs
   # at the bottom of .scrutinizer.yml.
   - 2.7
-  - 3.3
   - 3.4
   - 3.5
   - 3.6

README.md

@@ -9,7 +9,7 @@ connecting to and scripting Nvim processes through its msgpack-rpc API.
 
 #### Installation
 
-Supports python 2.7, and 3.3 or later.
+Supports python 2.7, and 3.4 or later.
 
 ```sh
 pip2 install neovim

neovim/api/nvim.py

@@ -36,6 +36,12 @@ class Nvim(object):
     `SubClass.from_nvim(nvim)` where `SubClass` is a subclass of `Nvim`, which
     is useful for having multiple `Nvim` objects that behave differently
     without one affecting the other.
+
+    When this library is used on python3.4+, asyncio event loop is guaranteed
+    to be used. It is available as the "loop" attribute of this closs. Note
+    that asyncio callbacks cannot make blocking requests, which which includes
+    accessing state-dependent attributes. They should instead schedule another
+    callback using nvim.async_call, which will not have this restriction.
     """
 
     @classmethod
@@ -90,6 +96,10 @@ def __init__(self, session, channel_id, metadata, types,
         self._decode = decode
         self._err_cb = err_cb
 
+        # only on python3.4+ we expose asyncio
+        if IS_PYTHON3:
+            self.loop = self._session.loop._loop
+
     def _from_nvim(self, obj, decode=None):
         if decode is None:
             decode = self._decode

neovim/msgpack_rpc/async_session.py

@@ -27,6 +27,7 @@ def __init__(self, msgpack_stream):
             1: self._on_response,
             2: self._on_notification
         }
+        self.loop = msgpack_stream.loop
 
     def threadsafe_call(self, fn):
         """Wrapper around `MsgpackStream.threadsafe_call`."""

neovim/msgpack_rpc/event_loop/__init__.py

@@ -2,15 +2,23 @@
 
 Tries to use pyuv as a backend, falling back to the asyncio implementation.
 """
-try:
-    # libuv is fully implemented in C, use it when available
-    from .uv import UvEventLoop
-    EventLoop = UvEventLoop
-except ImportError:
-    # asyncio(trollius on python 2) is pure python and should be more portable
-    # across python implementations
+
+from ...compat import IS_PYTHON3
+
+# on python3 we only support asyncio, as we want to expose it to plugins
+if IS_PYTHON3:
     from .asyncio import AsyncioEventLoop
     EventLoop = AsyncioEventLoop
+else:
+    try:
+        # libuv is fully implemented in C, use it when available
+        from .uv import UvEventLoop
+        EventLoop = UvEventLoop
+    except ImportError:
+        # asyncio(trollius on python 2) is pure python and should be more portable
+        # across python implementations
+        from .asyncio import AsyncioEventLoop
+        EventLoop = AsyncioEventLoop
 
 
 __all__ = ('EventLoop')

neovim/msgpack_rpc/msgpack_stream.py

@@ -19,20 +19,20 @@ class MsgpackStream(object):
 
     def __init__(self, event_loop):
         """Wrap `event_loop` on a msgpack-aware interface."""
-        self._event_loop = event_loop
+        self.loop = event_loop
         self._packer = Packer(encoding='utf-8',
                               unicode_errors=unicode_errors_default)
         self._unpacker = Unpacker()
         self._message_cb = None
 
     def threadsafe_call(self, fn):
         """Wrapper around `BaseEventLoop.threadsafe_call`."""
-        self._event_loop.threadsafe_call(fn)
+        self.loop .threadsafe_call(fn)
 
     def send(self, msg):
         """Queue `msg` for sending to Nvim."""
         debug('sent %s', msg)
-        self._event_loop.send(self._packer.pack(msg))
+        self.loop .send(self._packer.pack(msg))
 
     def run(self, message_cb):
         """Run the event loop to receive messages from Nvim.
@@ -41,12 +41,12 @@ def run(self, message_cb):
         a message has been successfully parsed from the input stream.
         """
         self._message_cb = message_cb
-        self._event_loop.run(self._on_data)
+        self.loop .run(self._on_data)
         self._message_cb = None
 
     def stop(self):
         """Stop the event loop."""
-        self._event_loop.stop()
+        self.loop .stop()
 
     def _on_data(self, data):
         self._unpacker.feed(data)

neovim/msgpack_rpc/session.py

@@ -26,6 +26,7 @@ def __init__(self, async_session):
         self._pending_messages = deque()
         self._is_running = False
         self._setup_exception = None
+        self.loop = async_session.loop
 
     def threadsafe_call(self, fn, *args, **kwargs):
         """Wrapper around `AsyncSession.threadsafe_call`."""

setup.py

@@ -7,15 +7,13 @@
 install_requires = [
     'msgpack>=0.5.0',
 ]
-extras_require = {
-    'pyuv': ['pyuv>=1.0.0'],
-}
 
-if os.name == 'nt':
-    install_requires.append('pyuv>=1.0.0')
-elif sys.version_info < (3, 4):
-    # trollius is just a backport of 3.4 asyncio module
-    install_requires.append('trollius')
+if sys.version_info < (3, 4):
+    if os.name == 'nt':
+        install_requires.append('pyuv>=1.0.0')
+    else:
+        # trollius is just a backport of 3.4 asyncio module
+        install_requires.append('trollius')
 
 if platform.python_implementation() != 'PyPy':
     # pypy already includes an implementation of the greenlet module
@@ -32,5 +30,4 @@
       packages=['neovim', 'neovim.api', 'neovim.msgpack_rpc',
                 'neovim.msgpack_rpc.event_loop', 'neovim.plugin'],
       install_requires=install_requires,
-      extras_require=extras_require,
       zip_safe=False)