Serve files from prod if not found locally

gistfile1.apacheconf

  # Serve files from prod if not available locally per:
 # https://docs.acquia.com/articles/serving-files-production-development-environments
  #
  # If the request is to the files directory
  RewriteCond %{REQUEST_URI} ^/sites/default/files/(.*)$
  # If we are not on prod
  RewriteCond %{ENV:AH_SITE_ENVIRONMENT} !^prod
  # If we are not on stage
  RewriteCond %{ENV:AH_SITE_ENVIRONMENT} !^test
  # If the file or directory is not found
  RewriteCond %{REQUEST_FILENAME} !-f 
  RewriteCond %{REQUEST_FILENAME} !-d 
  # Then redirect the request to the production server
  RewriteRule ^sites/default/files/(.*)$ http://example.com/sites/default/files/$1 [L]