I manually disabled xxlimited (file xxlimited.c removed , and lines in setup.py  commented) because : 

In file included from ./Include/Python.h:68,
                 from xxxx/build/python3-3.4.2/Modules/xxlimited.c:17:
./Include/object.h:65:2: error: #error Py_LIMITED_API is incompatible with Py_DEBUG, Py_TRACE_REFS, and Py_REF_DEBUG

So python has been rebuilt with option  -with-pydebug 
Now, I don't have segfault thanks to assert of line 821

#python
python: Objects/dictobject.c:821: insertdict: Assertion `ep->me_key != ((void *)0) && ep->me_key != (&_dummy_struct)' failed.
Aborted

buildroot-2015.02 set the following configuration options :
./configure --target=arm-buildroot-linux-gnueabi --host=arm-buildroot-linux-gnueabi --build=x86_64-unknown-linux-gnu --prefix=/usr --exec-prefix=/usr --sysconfdir=/etc --localstatedir=/var --program-prefix=""     --enable-ipv6  --enable-shared  --disable-curses --with-libmpdec=none --with-expat=none --enable-old-stdlib-cache --disable-sqlite3 --disable-codecs-cjk --disable-ossaudiodev --with-pydebug --without-ensurepip --without-cxx-main --with-system-ffi --disable-pydoc --disable-test-modules --disable-lib2to3 --disable-tk --disable-nis --disable-idle3 –disable-pyo-build