🐝 Add preflight check for "make sync-images"

It now checks if you have installed the AWS CLI, and whether you have
configured it, before letting you proceed.

Makefile

@@ -130,6 +130,8 @@ migrate:
 	@echo '==> Running DB migrations'
 	yarn && yarn buildTsc && yarn runDbMigrations
 
+refresh.full: refresh refresh.wp sync-images
+
 refresh:
 	@echo '==> Downloading chart data'
 	./devTools/docker/download-grapher-metadata-mysql.sh
@@ -153,11 +155,16 @@ refresh.wp:
 	@echo '[email protected] user to the value from `.env:WORDPRESS_API_PASS`'
 	@echo 'at https://staging.owid.cloud/wp/wp-admin/user-edit.php?user_id=35'
 
-sync-images:
+sync-images: sync-images.preflight-check
 	@echo '==> Syncing S3 images'
 	@. ./.env && ./devTools/docker/sync-s3-images.sh
 
-refresh.full: refresh refresh.wp sync-images
+sync-images.preflight-check:
+	@echo '==> Checking for aws cli'
+	@which aws >/dev/null 2>&1 || (echo "ERROR: please install aws cli -- e.g. brew install awscli"; exit 1)
+	@echo '==> Checking if aws cli is configured'
+	@test -f ~/.aws/config || (echo "ERROR: please configure aws cli -- e.g. aws configure"; exit 1)
+
 
 down:
 	@echo '==> Stopping services'