ITK 5.0 only supports Python 2.7 on Linux and macOS because of limitations of the C++ compiler required for Python 2.7 on Windows.
Are there any objections to only supporting Python 3.5 and newer on all platforms with ITK 5.1?
As pointed out by @hjmjohnson, many packages in the Scientific Python community only support Python 3.5 and newer in their latest versions, Python 2 support itself is ending in 2020, and this will reduce our maintenance version.
I am fully in support of requiring python 3.5. The focus on a smaller subset environments will allow for using our precious resources for the most benefit.
Following up, based on support for this proposal, ITK will only be supporting Python 3 with 5.1.0 and later.
Continuous integration testing on all platforms now uses Python 3. A warning will be issued if a build tries to use Python 2. There are already a few false positive test failures if Python 2 is used on Git master, but this will reduce our maintenance burden going forward.