Issues on PyPy

I'm trying to use this in a PyPy environment with psycopg2cffi installed; however, I get this error:
```
File "project/lib/foo/src/foo/foo.py", line 5, in
from aiopg.sa.engine import Engine
File "/usr/local/site-packages/aiopg/__init__.py", line 6, in
from .connection import connect, Connection, TIMEOUT as DEFAULT_TIMEOUT
File "/usr/local/site-packages/aiopg/connection.py", line 12, in
import psycopg2
ModuleNotFoundError: No module named 'psycopg2'
```

If I try to do the `psycopg2cffi.compat.register()` monkeypatch thing, I get this error:

```
Fatal error on aiopg connection: POLL_ERROR from underlying .poll() call\nconnection:
```

Are there instructions for installing into PyPy (if so, apologies for missing them)? Am I doing something wrong? Or maybe this simply isn't supported?