I'm trying to compile a simple kivy app into an apk but I keep getting this error: error: unknown file type '.pxi' (from 'jnius/jni.pxi'). I believe the issue is cython but I don't know how to fix it. I've tried using different cython versions (0.25, 0.26 and 0.27).
Full log - https://jpst.it/17EwW
I discussed this error with another user, but never worked out quite what the issue is. However, their problems were eventually resolved by making sure Kivy and python-for-android were up to date. In this case, you could try changing kivy to kivy==master in the buildozer.spec requirements line, then cleaning everything and trying the build again.
It may also help to make sure your cython version is 0.25 or 0.26, although I think any recent version should work with Kivy master.