Python ./configure does not find g++ compiler

Workaround:

CXX=/usr/bin/g++ ./configure

Anyway it's very strange and it seems to be a bug in the configure script. It seems to be a known problem. Oh well...

EDIT: It seems that --with-cxx-main is an option with a different purpose. It's required on some platforms to support C++ extension modules. I updated my answer above.

You can set the location of g++ manually using an environment variable passed to configure, as described in the help:

Usage: ./configure [OPTION]... [VAR=VALUE]...

For example, if you are running configure with a custom prefix your command would be:

./configure --prefix=/home/user/.local CXX="/usr/bin/g++"