Improve debugging experience

[faroit]

Currently the debugging experience of the io.download_single function is not idea since its inside of an async task. If an exception is raised inside of that function tasks are not stopped, thus makes is hard to debug it.

I added a watchdog decorator, but it doesn't work in all cases yet:

gbif-dl/gbif_dl/utils.py

Lines 5 to 17 in 3f2707a

	def watchdog(afunc):
	"""Stops all tasks if there is an error"""
	@functools.wraps(afunc)
	async def run(*args, **kwargs):
	try:
	await afunc(*args, **kwargs)
	except asyncio.CancelledError:
	return
	except Exception as err:
	print(f'exception {err}')
	asyncio.get_event_loop().stop()
	return run