Python 3.5 reaches its end-of-life in a few weeks: https://www.python.org/downloads/release/python-3510/. Once it does, we should drop support for running pytype under 3.5 so that we can use modern features like f-strings and variable annotations.

For now, we won't deliberately break analyzing code as 3.5, but users will need two interpreters - a 3.5 one to compile bytecode for the code under analysis, and a 3.6-3.8 one to run pytype - and support will degrade over time once we remove the tests. (Of course, it's always possible to pin to an older version of pytype.)