Like an abstract class that requires you subclass certain methods but for settings. Just a thought

gistfile1.py

class LazyNotImplementedError:
    def __init__(self, error_msg):
        self.error_msg = error_msg
    def __call__(self, *__):
        raise NotImplementedError(self.error_msg)
    __str__ = __add__ = __call__

# settings.py example
BASE = LazyNotImplementedError("You must set this in your settings_local")

# tests
try:
    BASE + "/"
except NotImplementedError:
    pass
try:
    print BASE
except NotImplementedError:
    pass
try:
    import os
    os.path.join(BASE, '/')
except NotImplementedError:
    pass
try:
    print unicode(BASE)
except NotImplementedError:
    pass
try:
    print repr(BASE)
except NotImplementedError:
    pass