Python 3.8 is out for a while, so it would be nice if atomicwrites support it.
I ran the tests locally with Python 3.8, no errors, not even a deprecation warning.
If you are ok, I'd create a pull request to add support for Python 3.8.
I'd also clean up the current version mismatches:
$ check-python-versions
setup.py says: 2.7, 3.4, 3.5, 3.6, 3.7
- python_requires says: 2.7, 3.4, 3.5, 3.6, 3.7, 3.8
tox.ini says: 2.7, 3.4, 3.5, 3.6, 3.7, 3.8, PyPy
.travis.yml says: 2.7, 3.4, 3.5, 3.6, 3.7, PyPy
mismatch!
Also, I noticed, in appveyor you only test up to Python 3.6, and only the 32 bit executables. If you are ok, I'd add also the 64 bit versions.
Thanks for your work!
P.S.: What do you think about dropping support for Python 3.4?