LibEvConnection: Avoid dict.keyview in Python 3.
LibEvConnection: Avoid dict.keyview in Python 3.

Turns out that the following code is flawed:

    stuff = a_dict.keys()
    for key in stuff:
        del a_dict[key]

It raises an "collection modified during iteration" exception since
`dict.keys()` does not return a list of keys.  It returns an iterable
that is attached to the underlying collection :/

vitaly-krugl/pika,Zephor5/pika,pika/pika,zixiliuyue/pika,knowsis/pika