[CMake] How to find Python 2.7 libraries if 3.x is installed too

[René J.V. Bertin]

Hello,

I am trying to get a not-so-old project to build (gizmod.sourceforge.net) which requires Python2.7 and libboost-python. 
I cannot seem to figure out how to do a find_package(PythonLibs REQUIRED) that will not consider that Python 3.4 is a suitable newer version of Python 2.7 . Is that even possible? The documentation in FindPythonLibs.cmake suggests that one can limit the search to specific versions, but that doesn't work.
And using find_package(PythonLibs 2.7.5 EXACT REQUIRED) raises an error because it too finds v3.4 ...

Thanks,
R.B.