# File lib/phusion_passenger/platform_info/apache.rb, line 139
        def self.httpd_default_error_log(options = nil)
                if info = httpd_V(options)
                        info =~ /-D DEFAULT_ERRORLOG="(.+)"$/
                        filename = $1
                        if filename =~ /\A\//
                                return filename
                        else
                                # Not an absolute path. Infer from root.
                                if root = httpd_root(options)
                                        return "#{root}/#{filename}"
                                else
                                        return nil
                                end
                        end
                else
                        return nil
                end
        end