First anniversary sprint

See details here: https://python-sprints.github.io/london/2018/09/18/first-anniversary.html

In case of waiting list, we give priority to (let us know if it's you):

• People from underrepresented minorities in IT
• Maintainers of open source packages
• Supporting members of NumFOCUS or the PSF (consider making a donation and becoming one if you're not)
• People visiting from abroad