CentOS

Action:

yum install httpd mod_ssl

httpd -t

Result:

AH00526: Syntax error on line 85 of /etc/httpd/conf.d/ssl.conf:
SSLCertificateFile: file '/etc/pki/tls/certs/localhost.crt' does not exist or is empty

Looks like that's a change that now requires you to generate your own self signed cert (or a real one) rather than using a generic "snake-oil" one like previous releases.

I just checked. In CentOS 7, installing mod_ssl creates /etc/pki/tls/certs/localhost.crt and /etc/pki/tls/private/localhost.key for you.