[patch] Check for file permissions for proper error messages

[Tim]

I'm not sure how possible it is, but sometimes the error messages (eg TemplateDoesNotExist) don't reflect the correct problem. I've had a few times where it was simply a case of the apache user not being able to read the files, but the error message meant that I was looking at the problem from the wrong persective.

Would this be hard / worthwhile to implement? Maybe even at a basic level it could tell the user in the error message to check permissions?

[tbarta@…]

patch to generate a different exception type when a file is found but unreadable

[tbarta@…]

I don't know much about the template loading system, but this patch should generate a different exception if a file is found in the template path, but could not be read due to access permissions. The exception raised is a subclass of TemplateDoesNotExist, so try/except blocks elsewhere in the code should work. I am not sure about the errno module's cross-compatibility... does anyone know if this will work with Windows or OS X?

[Jacob]

I think adding the extra exception just makes the code more cluttered -- this is a pretty easy problem to figure out and diagnose.