Add pytest-celery to the list of test dependencies (#270)

Author: Andrey Slotin

setup.py

@@ -108,6 +108,7 @@ def check_setuptools():
               'pymongo>=3.7.0',
               'pyramid>=1.2',
               'pytest>=4.6',
+              'pytest-celery',
               'redis>3.0.0',
               'requests>=2.17.1',
               'sqlalchemy>=1.1.15',