I may be doing something wrong, but I have been trying to install pyside on Mac 10.12 (Sierra). Here is what I tried (after installing Qt with brew):
You need a specific version of Qt and pyside.
Install both the QT 4.8.5 package as well as pyside from the Mac installers on the page below:
https://wiki.qt.io/PySide_Binaries_MacOSX