This is not expected, but I don't know where the problem is.

On my machine I get:

>>> socket.gethostbyname('0.1.1.~1')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
socket.gaierror: [Errno 8] nodename nor servname provided, or not known

This is on a machine running 10.13.6:

$ sw_vers
ProductName:	Mac OS X
ProductVersion:	10.13.6
BuildVersion:	17G65

I'm using a checkout of master of about a week all, and get the same exception with 3.7.0.  I also get the same exception on the current beta of macOS 10.14 (With python 3.7.0)

I'm currently building the current master to check if that changes anything.