Can we use f-strings?

[rwest]

I think Travis is testing compatibility with Python 3.5 which means we can't use f strings. May we increase the minimum requirements to Python 3.6? Or would that exclude a lot of hypothetical users?

[kyleniemeyer]

I personally think it’s reasonable to say Python 3.6+, considering how easy it is now to set up an environment in Anaconda. And the latest version is 3.7, so supporting the most recent two seems ok, as long as it’s clear in the docs.

[bryanwweber]

My only mild concern is that the default Python 3 in Ubuntu 16.04 is 3.5, and that will have support through 2021. The official end of life for 3.5 isn't until September 2020 as well. Not everyone will have/want to use Anaconda...