Since March 2020 all new projects on Scrapy Cloud will use a Scrapy Stack that runs on top of Python 3 by default.
If you existing project is still running on an older Scrapy Stack, please make sure to update your project's deploy settings, on scrapinghub.yml, file to use a newer stack that bases on Python 3:
stacks: default: scrapy:1.6-py3
Note: All stack version from 2.0 and later already use Python 3 as a default, to the -py3 suffix is no longer required.
For more information on which stack version support Python 3, you can check GitHub repository for Scrapy Stacks, and for further reading on the deploy environment, please see Changing the Deploy Environment With Scrapy Cloud Stacks.