@tribedude's admin here...
The error message is because PHP 5.4.16 is installed (CentOS' latest version), and so it's blocking the XF2 upgrade.
Current:
CentOS 7.6
PHP 5.4.16
MPM: Prefork
MySQL (Percona) on same host
XF 1.5.10
Interim:
CentOS 7.6
PHP 5.4.16 (CentOS repo) and PHP 7.3.7...