ImportError: Failed to import libcppyy3_7. Please check that ROOT has been built for Python 3.7

[Mark_C_Hodgkinson]

So it seems its not possible to build 6.22.02 at all on mac os currently. I get the somewhat similar errors as seen here:

Build error on MacOS, macports... with unctrl.h / ncurses.h

Dear All, I am having problems building ROOT 6.22.00 from source on macOS. Note, my (ultimate) aim here is to update the build within MacPorts, so I am building with a number of dependencies required by that build installed in the usual MacPorts prefix, /opt/local. The build errors however can be reproduced outside MacPorts using a simple cmake build i.e. git clone git@github.com:root-project/root.git cd root git checkout v6-22-00-patches cd .. mkdir build cd build cmake ../root cmake --build…

Trying the solution of dropping back to 6.20.06 works, but that version does not seem to support python3. At least I could not find any way to get it to build with python3 instead of python2. Is there some way? The instructions mention setting PYTHON_EXECUTABLE:

Building ROOT from source

but this made no difference in my case. cmake still tries to use python 2.7.

Cheers,

Mark