Add proper message/exit in case of a connection error

admin.py

@@ -253,7 +253,12 @@ def connected_as(data):
 
 printv('connecting to '+API_URL+'...')
 printv('login user '+os.environ['QCM_USER_NAME']+'...')
-sio.connect(API_URL, transports=['websocket'], namespaces=['/'], wait_timeout = 20)
+try:
+    sio.connect(API_URL, transports=['websocket'], namespaces=['/'], wait_timeout = 20)
+except socketio.exceptions.ConnectionError as e:
+    print('Cannot connect to {}\n{}'.format(API_URL, e), file=sys.stderr)
+    exit(1)
+
 sio.emit('verify', os.environ['QCM_USER_NAME']+':'+os.environ['QCM_USER_TOKEN'])
 
 sio.wait()