added import fix for django 1.4 exceptions

In django 1.4, the [exception](https://docs.djangoproject.com/en/1.4/ref/exceptions/#suspiciousoperation) was known as `SuspiciousOperation` instead of `SuspiciousFileOperation`.

I added an (meta?) exception for the import error which will import the 1.4 version as the class name used in the `generator.py` code.