Sure, but why not support it in an external facing product? No one externally depends on that old google code.
Started as an internal tool, at least according to medium & other blog posts.
It is in the works [0], and like people said since Google uses Python 2.7 that's the verison that was supported by default.
[0] https://stackoverflow.com/questions/46941308/python-3-suppor...
They can release a version that supports 2.7 much sooner
It's just a lot of code to migrate. It takes time.
Disclaimer: Work at Google, wrote some of that code.