Support python2.7.18

[renyijiu]

• Argument

python2.7.18 strictyaml==1.6.2

• Bug

When i test the package with python2.7.18, it raise error when import, so does this package support python2.7.18? if not, should update the setup.py.

[hyunlee1o]

Why would you still support python 2?

[crdoconnor]

yeah, I dropped python 2 support a while back but I think I might have forgotten to update the tags.