asyncio support

[mdavidsaver]

I would find it useful if inotify integrated with asyncio.

Here is a quick example of what would be involved. Although I think an actual implementation should be done quite differently.

import asyncio
import os
import sys

from inotify.adapters import Inotify, _DEFAULT_TERMINAL_EVENTS, TerminalEventException
import inotify.constants as Iconst

class AInotify(Inotify):
    def __init__(self, *args, **kws):
        super().__init__(*args, **kws)

    def fileno(self):
        return self._Inotify__inotify_fd

    async def aevent_gen(self, terminal_events=_DEFAULT_TERMINAL_EVENTS):
        loop = asyncio.get_running_loop()
        try:
            while True:
                ready = loop.create_future()
                # replaces previous reader for this FD
                loop.add_reader(self.fileno(), ready.set_result, None)

                await ready

                # _handle_inotify_event() calls read(fd) exactly once,
                # so we can get away with not setting FD to non-blocking
                for (header, type_names, path, filename) in self._handle_inotify_event(self.fileno()):
                    e = (header, type_names, path, filename)
                    for type_name in type_names:
                        if type_name in terminal_events:
                            raise TerminalEventException(type_name, e)

                    yield e

        finally:
            loop.remove_reader(self.fileno())