After hacking the configure script to work around the issues http://bugs.python.org/issue4025 and http://bugs.python.org/issue1633863 
the build still fails:

building 'fcntl' extension
xlc_r -DNDEBUG -O -I. -I/home/u0006584/Python-2.6/./Include -I. -
IInclude -I./Include -I/home/u0006584/Python-2.6/Include -
I/home/u0006584/Python-2.6 -c /home/u0006584/Python-
Modules/fcntlmodule.c -o build/temp.aix-6.1-
2.6/home/u0006584/Python-2.6/Modules/fcntlmodule.o
./Modules/ld_so_aix xlc_r -bI:Modules/python.exp build/temp.aix-6.1-
2.6/home/u0006584/Python-2.6/Modules/fcntlmodule.o -o build/lib.aix-6.1-
2.6/fcntl.so
ld: 0711-317 ERROR: Undefined symbol: .flock
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more 
information.
*** WARNING: renaming "fcntl" since importing it failed:        0509-022 
Cannot load module build/lib.aix-6.1-2.6.
        0509-026 System error: A file or directory in the path name does 
not exist.
error: No such file or directory
make: 1254-004 The error code from the last command is 1.

(Full transcript attached)

I'm mystified and I can't log in to the AIX box right now.

This does not appear to be the same as http://bugs.python.org/issue1756343 and http://bugs.python.org/issue1694442 which both appear to be the same, 
but documenting a differen AIX build problem.