2017-01-12 14:25:36 529 (ERROR): The installer was unable to verify that your kernel supports IPv6.
2017-01-12 14:25:36 530 (ERROR): The message received when trying to create an IPv6 socket was Address already in use
2017-01-12 14:25:36 531 (ERROR): Please ensure that the ipv6 module is enabled and loaded in your kernel.
2017-01-12 14:25:36 532 (FATAL): Exiting...
This happened in the middle of an install that I restarted. The only way to fix it was to restart the VPS/Server as certainly even older kernels support IPV6.