I edited the apache httpd.conf file recently for the mod_rewrite to work. I don\'t know if this problem originated from that or not, but i\'m getting this problem from that
Once, this happens to me as well. and when I googled the matter, I got to know that this happens when the permissions on the file is wrongfully set to 000 (which means that no one can read, write, or execute that file). Then I just changed my file permission privilege into Read & Write and it's worked for me.
To change file permission settings on mac: Right click on the particular file and click on Get info from dropdown menu and refer to the sharing and permissions panel and change privilege settings into Read & Write
More: http://www.itoctopus.com/warning-unknown-failed-to-open-stream-permission-denied-in-unknown-on-line-0-error-in-joomla