Unable to build PySide on linux against 5.6.x

I'm unable to complete a PySide2 build against Qt 5.6.0 or 5.6.1-1 on 64 bit linux. Build stops at QtWebEngineWidgets phase.

System being used:

Linux: Debian Jessie, on 2 machines.
Qt: 5.6.0 and 5.6.1-1 64 bit installed to home.
Python: Virtual Env of system's packaged Python 3.4 (3.4.2).

Error message:
[ 97%] Running generator for QtWebEngineWidgets...
Fatal error: line=26, column=66, message=Failed to parse: 'typesystem_webchannel.xml'

Cannot parse file: /home/lars/pyside-setup/sources/pyside2/PySide2/QtWebEngineWidgets/typesystem_webenginewidgets.xmlPySide2/QtWebEngineWidgets/CMakeFiles/QtWebEngineWidgets.dir/build.make:53: recipe for target 'PySide2/QtWebEngineWidgets/PySide2/QtWebEngineWidgets/qwebenginecertificateerror_wrapper.cpp' failed
make[2]: *** [PySide2/QtWebEngineWidgets/PySide2/QtWebEngineWidgets/qwebenginecertificateerror_wrapper.cpp] Error 1
CMakeFiles/Makefile2:1245: recipe for target 'PySide2/QtWebEngineWidgets/CMakeFiles/QtWebEngineWidgets.dir/all' failed
make[1]: *** [PySide2/QtWebEngineWidgets/CMakeFiles/QtWebEngineWidgets.dir/all] Error 2
Makefile:117: recipe for target 'all' failed
make: *** [all] Error 2
error: Error compiling pyside2