This was very carefully considered. A blog post explaining all of the design decision will be published in the near future.
Essentially, I wanted to use setup.cfg's new 'requires-python' directive. However, distutils2 has been stalled and its future is in question. Distlib was also considered, but it's also quite controversial.
There are some other exciting Python packaging projects being developed actively that seek to solve these problems. We plan to support these standards when the time is right. In the meantime, a simple runtime.txt file suits everyone's needs perfectly.
Essentially, I wanted to use setup.cfg's new 'requires-python' directive. However, distutils2 has been stalled and its future is in question. Distlib was also considered, but it's also quite controversial.
There are some other exciting Python packaging projects being developed actively that seek to solve these problems. We plan to support these standards when the time is right. In the meantime, a simple runtime.txt file suits everyone's needs perfectly.