The PYTHONHOME variable does not allow complete control over making a
Python installation find its own libs because "lib/pythonX.Y" gets
appended to it, see:
    http://docs.python.org/using/cmdline.html#envvar-PYTHONHOME

For example, let's say my Python installation is here:
    /home/soundmurderer/lib/x86_64/python2.6

I cannot set PYTHONHOME to point to this, because my path does not end
in "lib/pythonX.Y".  Of course, you could say that I should just move
the Python libs, but it may create inconsistencies on how stuff is
organized on some systems.  PYTHONHOME should point to the Python
installation root, period.  Please give the admin complete control.

Also, the --libdir flag to ./configure should work and set PYTHONHOME
correctly.  The fact that it does nothing has its own ticket, see:
    http://bugs.python.org/issue858809

It is, however, my humble opinion that fixing that other ticket properly
also necessitates fixing how PYTHONHOME works (because --libdir should
set the default PYTHONHOME during build/install), so they should really
be one issue.

Thanks!