Bump up the python version requirement to match reality

- Python >= 2.6 is known to work, 2.5 might be possible with __future__
  imports but until somebody tests it...

configure.ac

@@ -670,9 +670,7 @@ esac],
 [enable_python=no])
 
 AS_IF([test "$enable_python" = yes],[
-# rpm-python is based on python-2.5, 
-# with legacy hacks to allow building against python >= 2.3
-  AM_PATH_PYTHON([2.3],[
+  AM_PATH_PYTHON([2.6],[
     WITH_PYTHON_INCLUDE=`${PYTHON} -c 'from distutils.sysconfig import *; import sys; sys.stdout.write(get_python_inc())'`
     WITH_PYTHON_SUBPACKAGE=1
     save_CPPFLAGS="$CPPFLAGS"