issue#25825 is closed - and had python2.7 removed - so, want to mention there is something broken - a long time it would seem on AIX - for building packages after python and ensurepip are installed.

Currently trying to pip install mercurial; later a regular "make build"

PIP INSTALL

    running build_ext
    building 'mercurial.base85' extension
    creating build/temp.aix-5.3-2.7
    creating build/temp.aix-5.3-2.7/mercurial
    xlc_r -I/opt/include -I/opt/buildaix/include -O2 -DNDEBUG -O -I/opt/include/python2.7 -c mercurial/base85.c -o build/temp.aix-5.3-2.7/mercurial/base85.o
    ./Modules/ld_so_aix xlc_r -bI:./Modules/python.exp build/temp.aix-5.3-2.7/mercurial/base85.o -o build/lib.aix-5.3-2.7/mercurial/base85.so
    unable to execute './Modules/ld_so_aix': No such file or directory
    error: command './Modules/ld_so_aix' failed with exit status 1

    ----------------------------------------
    Command "/opt/bin/python -c "import setuptools, tokenize;__file__='/tmp/pip-build-zmElG2/mercurial/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-0lo0Bk-record/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /tmp/pip-build-zmElG2/mercurial

MAKE BUILD
root@x064:[/data/prj/python/mercurial/mercurial-3.9.1]/opt/bin/make PREFIX=/opt/ build
python setup.py  build
running build
running build_mo
running build_py
copying mercurial/__modulepolicy__.py -> build/lib.aix-5.3-2.7/mercurial
running build_ext
building 'mercurial.base85' extension
xlc_r -I/opt/include -I/opt/buildaix/include -O2 -DNDEBUG -O -I/opt/include/python2.7 -c mercurial/base85.c -o build/temp.aix-5.3-2.7/mercurial/base85.o
./Modules/ld_so_aix xlc_r -bI:./Modules/python.exp build/temp.aix-5.3-2.7/mercurial/base85.o -o build/lib.aix-5.3-2.7/mercurial/base85.so
unable to execute './Modules/ld_so_aix': No such file or directory
error: command './Modules/ld_so_aix' failed with exit status 1
Makefile:55: recipe for target 'build' failed
make: *** [build] Error 1


Problem seems to be in _sysconfigdata.py

root@x064:[/opt/lib/python2.7]grep ld_so_aix *.py
_sysconfigdata.py: 'BLDSHARED': './Modules/ld_so_aix xlc_r -bI:./Modules/python.exp',
_sysconfigdata.py: 'LDCXXSHARED': '/opt/lib/python2.7/config/ld_so_aix xlc_r -bI:/opt/lib/python2.7/config/python.exp',
_sysconfigdata.py: 'LDSHARED': './Modules/ld_so_aix xlc_r -bI:./Modules/python.exp',

SOLUTION:
set LDSHARED to same value as LDSHARED, i.e.,
'LDSHARED': '/opt/lib/python2.7/config/ld_so_aix xlc_r -bI:/opt/lib/python2.7/config/python.exp'

If this has already be done for Python2.7 - then perhaps issue#25825 should have Python2.7 restored - and this closed.

Otherwise - please repair.