Setup error with Psr\\Log package

Downloaded the latest this morning, copied it over to the server and ran it, got the Whoops page, checked the logs, found this:

Code:

[Mon May 29 14:31:46.307201 2017] AH01215: PHP Fatal error:  Interface 'Psr\\Log\\LoggerInterface' not found in /***mypath***/system/Log/Logger.php on line 55: /usr/local/cpanel/cgi-sys/ea-php70

Best I can figure out searching online is that I don't have the Psr\Log package installed, which I believe is a PHP package (and not an Apache one). My "easyApache4" setup doesn't give me options to select anything remotely connected to the package name.

Pointers in the right direction to resolve this?