[isssue #25] add except for socket.gaierror

pyheatpump/cli.py

 import json
 import os
 import re
+import socket
 import sys
 import time
 import urllib
         **{'path': get_path}
     }
 
-    get_resp = requests.get(
-        url=build_url(get_url),
-        verify=False
-    )
+    try:
+        get_resp = requests.get(
+            url=build_url(get_url),
+            verify=False
+        )
+    except socket.gaierror as exc:
+        logger.error('Socket error : %s', exc)
+        sys.exit(-1)
 
     control_data = get_resp.json()
     if Heatpump(mac_address).control(control_data):