keepalive: add `__repr__()` to the HTTPConnection class to ease debugging By default, this just printed the class name and memory address. By displaying the address and ports on both sides of the socket, it makes it easier to figure out what's in the ConnectionManager, and correlate with WireShark traces. It looks like the two connections mentioned in the previous commit come about because the LFS POST request to access the blobs opens connection 1, and gets a 401. Then for some reason, the follow up with credentials opens a new socket, instead of using the existing one in the pool. I have no clue why. This can be seen with something like this in the blobstore: ``` for h in self.urlopener.handlers: if hasattr(h, "close_all"): print('open connections on %s in pid %d' % (type(h), os.getpid())) for host, conns in h._cm.get_all().items(): for c in conns: print('connection: %r' % c) ```