py-pyqt5 and qt56

[db]

How can I install py-pyqt5 with an older version of qt5?
There are subports for python but not for qt.

$ sudo port install py-pyqt5
Password:
--->  Computing dependencies for py-pyqt5
Error: Can't install qt5-qtscript because conflicting ports are active: qt56-qtbase
Error: Follow https://guide.macports.org/#project.tickets to report a bug.
Error: Processing of port py-pyqt5 failed