Searches "django.core" and the apps in settings.INSTALLED_APPS to find the
    named command class, optionally skipping packages or a particular
    command class.

def get_command_class(name, exclude_packages=None, exclude_command_class=None):
    """
    Searches "django.core" and the apps in settings.INSTALLED_APPS to find the
    named command class, optionally skipping packages or a particular
    command class.
    
    """
    from django.conf import settings
    return get_command_class_from_apps(
        name, 
        settings.INSTALLED_APPS \
            if "django.core" in settings.INSTALLED_APPS \
            else ("django.core",) + tuple(settings.INSTALLED_APPS),
        exclude_packages=exclude_packages,
        exclude_command_class=exclude_command_class)