Working with absolute path on Pantheon.

path.md

Wrong way

define( 'WPCACHEHOME', '/srv/bindings/12345678905432167890/code/wp-content/plugins/wp-super-cache/' );

Proper way

define( 'WPCACHEHOME', $_SERVER["DOCUMENT_ROOT"] . '/wp-content/plugins/wp-super-cache/');

or

if ( defined( 'PANTHEON_BINDING' ) ):
    define( 'WPCACHEHOME', sprintf('/srv/bindings/%s/code/wp-content/plugins/wp-super-cache/', PANTHEON_BINDING));
endif;