Bump celery to 4.1.1 (#5134)

* Bump celery to 4.1.1

Docs reference `celery worker --app=superset.sql_lab:celery_app
--pool=gevent -Ofair` command which seems only to work with Celery 4.1.1

* Add UPDATING.md message

UPDATING.md

@@ -3,6 +3,12 @@
 This file documents any backwards-incompatible changes in Superset and
 assists people when migrating to a new version.
 
+## Superset 0.26.0
+* Superset 0.26.0 deprecates the `superset worker` CLI, which is a simple
+wrapper around the `celery worker` command, forcing you into crafting
+your own native `celery worker` command. Your command should look something
+like `celery worker --app=superset.sql_lab:celery_app --pool=gevent -Ofair`
+
 ## Superset 0.25.0
 Superset 0.25.0 contains a backwards incompatible changes.
 If you run a production system you should schedule downtime for this

requirements.txt

@@ -1,6 +1,6 @@
 bleach==2.1.2
 boto3==1.4.7
-celery==4.1.0
+celery==4.1.1
 colorama==0.3.9
 cryptography==1.9
 flask==0.12.2

setup.py

@@ -52,7 +52,7 @@ setup(
     install_requires=[
         'bleach',
         'boto3>=1.4.6',
-        'celery',
+        'celery>=4.1.1',
         'colorama',
         'contextlib2',
         'cryptography',