Add workaround for OS X issue.

qutebrowser/misc/ipc.py

@@ -360,8 +360,12 @@ def _has_legacy_server(name):
         log.ipc.debug("Socket error: {} ({})".format(
             socket.errorString(), err))
 
+    os_x_fail = (sys.platform == 'darwin' and
+                 socket.errorString() == 'QLocalSocket::connectToServer: '
+                                         'Unknown error 38')
+
     if err not in [QLocalSocket.ServerNotFoundError,
-                   QLocalSocket.ConnectionRefusedError]:
+                   QLocalSocket.ConnectionRefusedError] and not os_x_fail:
         return True
 
     socket.disconnectFromServer()