Merge pull request #1956 from pydanny/conditional-redis-merge

## Description

This is the same as the pull request #1693 with the master branch merged into it to avoid all the extra unrelated commits which are already in master. Looks like Github is getting confused due to a rebase on that branch, which make that PR hard to review...

## Rationale

See #1693 - Locally, Redis is necessary only if Celery is used, while in Production it's also used for Caching.

## Use case(s) / visualization(s)

Fixes #1691

{{cookiecutter.project_slug}}/.envs/.local/.django

@@ -3,10 +3,11 @@
 USE_DOCKER=yes
 IPYTHONDIR=/app/.ipython
 
+{%- if cookiecutter.use_celery == 'y' %}
 # Redis
 # ------------------------------------------------------------------------------
 REDIS_URL=redis://redis:6379/0
-{% if cookiecutter.use_celery == 'y' %}
+
 # Celery
 # ------------------------------------------------------------------------------
 

{{cookiecutter.project_slug}}/compose/production/django/entrypoint

@@ -5,8 +5,10 @@ set -o pipefail
 set -o nounset
 
 
+{% if cookiecutter.use_celery == 'y' %}
 # N.B. If only .env files supported variable expansion...
 export CELERY_BROKER_URL="${REDIS_URL}"
+{% endif %}
 
 if [ -z "${POSTGRES_USER}" ]; then
     base_postgres_image_default_user='postgres'