Remove test_enter_eventloop

[davidbrochart]

test_enter_eventloop does the following:

kernel.eventloop = asyncio.get_running_loop()

The only place where kernelbase.eventloop is used is here, and it seems to call the event loop. But an asyncio event loop is not callable, or am I missing something?
I inserted an error just before the call to the event loop, and the test still passes, so what does this test do?
Should we remove it?

[davidbrochart]

This last commit removes test_enter_eventloop.
If someone is against it, please speak up. Otherwise, I will merge.

[blink1073]

That test was there to add more coverage in enter_eventloop, I'm fine to remove it.