Use debian slim base image

.gitlab-ci.yml

@@ -13,8 +13,11 @@ beamer-build:
   tags: [build]
 
 synchronize:
-  image: chartedcode/alpine-sftp-client
+  image: debian:stable-slim
   stage: deploy
+  before_script:
+    - apt-get update -y
+    - apt-get install -y openssh-client sshpass
   script:
     - sshpass -p ${SFTP_PASSWORD} sftp -o StrictHostKeyChecking=no -P 2222 ${SFTP_USER}@${SFTP_HOST}:uploads <<< $'mkdir api\n cd api\n put *.pdf openpgp.pdf'
   dependencies: