Upgrade - call to undefined method error

I’ve put it in dev mode and checked my error logs but doesn’t quite explain anything for me, this is the only relevant error I have;

[Thu Mar 15 11:51:32.291377 2018] [core:error] [pid 971:tid 140516624623360] [client 192.168.81.1:65273] AH00037: Symbolic link not allowed or link target not accessible: /var/www/src/resources/silverstripe/framework/client/styles, referer: http://www.basestripe.pixel/Security/login/default/LoginForm/