available
Since Python 3.5, socket.socketpair() is now also available on Windows.
Make csock blocking before calling the accept() method, and fix also a typo in
an error message.
* Issue #159: Fix windows_utils.socketpair()
- Use "127.0.0.1" (IPv4) or "::1" (IPv6) host instead of "localhost", because
"localhost" may be a different IP address
- Reject also invalid arguments: only AF_INET/AF_INET6 with SOCK_STREAM (and
proto=0) are supported
* Reject add/remove reader/writer when event loop is closed.
* Fix ResourceWarning warnings