Should aiopg work correctly with connection_factory parameter?

Hi!

I want to use logical replication that's why I want to use connection_factory=LogicalReplicationConnection (`from psycopg2.extras import LogicalReplicationConnection`). I tried to debug app and I saw that psycopg2.connect initialized fine but code from method Connection._ready raised exception.

Without this parameter app works fine. Is it a bug?

Python 3.5.2
PostgreSQL (9.5.4)
Fedora release 24 (Twenty Four)

```
async def go():
async with aiopg.create_pool(dsn, connection_factory=LogicalReplicationConnection) as pool:
async with pool.acquire() as conn:
async with conn.cursor() as cur:
await cur.execute("SELECT 1")
async for row in cur:
print(row)
```

```
Traceback (most recent call last):
File "1.py", line 27, in
loop.run_until_complete(go())
File "/usr/lib64/python3.5/asyncio/base_events.py", line 387, in run_until_complete
return future.result()
File "/usr/lib64/python3.5/asyncio/futures.py", line 274, in result
raise self._exception
File "/usr/lib64/python3.5/asyncio/tasks.py", line 239, in _step
result = coro.send(None)
File "1.py", line 16, in go
async with aiopg.create_pool(dsn, connection_factory=LogicalReplicationConnection) as pool:
File "/home/budulianin/Documents/projects/pypgbus/pypgbus_venv/lib64/python3.5/site-packages/aiopg/utils.py", line 77, in __aenter__
self._obj = yield from self._coro
File "/home/budulianin/Documents/projects/pypgbus/pypgbus_venv/lib64/python3.5/site-packages/aiopg/pool.py", line 46, in _create_pool
yield from pool._fill_free_pool(False)
File "/home/budulianin/Documents/projects/pypgbus/pypgbus_venv/lib64/python3.5/site-packages/aiopg/pool.py", line 203, in _fill_free_pool
**self._conn_kwargs)
File "/home/budulianin/Documents/projects/pypgbus/pypgbus_venv/lib64/python3.5/site-packages/aiopg/utils.py", line 67, in __iter__
resp = yield from self._coro
File "/home/budulianin/Documents/projects/pypgbus/pypgbus_venv/lib64/python3.5/site-packages/aiopg/connection.py", line 83, in _connect
oids = yield from _enable_hstore(conn)
File "/home/budulianin/Documents/projects/pypgbus/pypgbus_venv/lib64/python3.5/site-packages/aiopg/connection.py", line 39, in _enable_hstore
""")
File "/home/budulianin/Documents/projects/pypgbus/pypgbus_venv/lib64/python3.5/site-packages/aiopg/cursor.py", line 113, in execute
yield from self._conn._poll(waiter, timeout)
File "/home/budulianin/Documents/projects/pypgbus/pypgbus_venv/lib64/python3.5/site-packages/aiopg/connection.py", line 237, in _poll
yield from asyncio.wait_for(self._waiter, timeout, loop=self._loop)
File "/usr/lib64/python3.5/asyncio/tasks.py", line 392, in wait_for
return fut.result()
File "/usr/lib64/python3.5/asyncio/futures.py", line 274, in result
raise self._exception
File "/home/budulianin/Documents/projects/pypgbus/pypgbus_venv/lib64/python3.5/site-packages/aiopg/connection.py", line 134, in _ready
state = self._conn.poll()
psycopg2.ProgrammingError: syntax error

Unclosed connection
connection:
```