Fix requirements, turn task into shared_task for compatibility

core/tasks/cron.py

@@ -1,10 +1,10 @@
-from celery import shared_task, task
+from celery import shared_task
 
 import logging
 
 logger = logging.getLogger(__name__)
 
-@task(name="cron")
+@shared_task(name="cron")
 def process_crons():
     from core.modules.cron import crondefinitions
     for definition in crondefinitions:

debian-packages.txt

@@ -1,3 +1,5 @@
 rabbitmq-server
 memcached
 git
+build-essential
+libmariadb-dev

requirements.txt

@@ -21,3 +21,4 @@ GitPython
 python-dateutil
 bindglobal
 pyotp
+pyqrcode