Support for `python_2_unicode_compatible` decorator removed in Django 3

[atlasstrategic]

@PiDelport I have tested this simple patch in my project successfully (Python version 3.6.6 and Django==3.0.2).

I have however not run the test suite nor have I removed the use of the six module, in case you still want to continue support for Python 2.

References

• I've found this Django commit rather useful. It shows how the Django maintainers removed the six module.
• As mentioned in Issue #14 the django-registration Django 3 support shows how they have removed the use of python_2_unicode_compatible.