pyuic6 error with layout alignment

I created the attached simple .ui file using Qt designer via the Qt for Python extension in VS Code.   When this .ui file is passed to uic using the following a parsing error is reported. 

pyuic6 mainwindow.ui -o MainWindow.py

.....   line 61, in _parse_alignment
    _, qt_align = qt_align.split('::')
    ^^^^^^^^^^^
ValueError: too many values to unpack (expected 2)

The main window has three widgets and I set the layout alignment of one of the widgets using designer.   The file is successfully parsed if I change the layout alignment of that widget to "no alignment".

.ui file and debug output of  pyuic6 attached.