Make sure that you have the request and i18n context processors included in the TEMPLATES['OPTIONS']['context_processors'] setting, as follows:

# settings.py or config/base.py
TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        # ...
        'OPTIONS': {
            'context_processors': [
                # ...
                'django.template.context_processors.request',
                'django.template.context_processors.i18n',
            ],
        },
    },
]

Also, create the utils app, if you haven't done so already, and place it under INSTALLED_APPS in the settings:

# settings.py or config/base.py
INSTALLED_APPS = [
    # ...
    'utils',
)