package/python-socketio: drop asgi/asyncio files for python 2.x to fix pycompile...

package/python-socketio: drop asgi/asyncio files for python 2.x to fix pycompile issue

socketio has conditional logic to load asgi/asyncio files when running under
Python 3.x:

if sys.version_info >= (3, 5):  # pragma: no cover
    from .asyncio_client import AsyncClient
    from .asyncio_server import AsyncServer
    from .asyncio_manager import AsyncManager
    from .asyncio_namespace import AsyncNamespace, AsyncClientNamespace
    from .asyncio_redis_manager import AsyncRedisManager
    from .asyncio_aiopika_manager import AsyncAioPikaManager
    from .asgi import ASGIApp
else:  # pragma: no cover
    AsyncClient = None
    AsyncServer = None
    AsyncManager = None
    AsyncNamespace = None
    AsyncRedisManager = None
    AsyncAioPikaManager = None

pycompile unfortunately errors out on these files when running under Python
2.x:

../scripts/pycompile.py ..
error:   File "/usr/lib/python2.7/site-packages/socketio/asyncio_server.py", line 84
    async def emit(self, event, data=None, to=None, room=None, skip_sid=None,
            ^
SyntaxError: invalid syntax

As a workaround, simply drop the unusable file from TARGET_DIR if building
for python 2.x.

Fixes:
http://autobuild.buildroot.net/results/455f3e09a590f7a6724ab8cd1b86bdf2bba8071a/

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>