Broken aiopg.sa.RowProxy unpacking

So RowProxy doesn't behave like the SQLAlchemy one, I find it really misleading.

```entry = {
'dtid': dtid,
'username': username,
}

query = psa.insert(User) \
.values(entry) \
.returning(User.c.id) \
.on_conflict_do_update(
index_elements=[User.c.dtid],
set_=entry
)
user_id = await (await conn.execute(query)).first()
print(type(user_id), user_id) # Output: " (1,)"
print(user_id[0]) # Output: " 1"
user_id, = user_id
print(user_id) # Output: " id"
```

As you see, everything goes well until I try to unpack the row...