socket.gaierror when no network connectivity

This error should be handled better:

```
Traceback (most recent call last):
File ".../env/lib/python3.5/site-packages/requests/packages/urllib3/connection.py", line 142, in _new_conn
(self.host, self.port), self.timeout, **extra_kw)
File ".../env/lib/python3.5/site-packages/requests/packages/urllib3/util/connection.py", line 75, in create_connection
for res in socket.getaddrinfo(host, port, family, socket.SOCK_STREAM):
File "/opt/boxen/pyenv/versions/3.5.2/lib/python3.5/socket.py", line 732, in getaddrinfo
for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno 8] nodename nor servname provided, or not known
```