Also is an issue with 3.5.1-r3:

x86_64-pc-linux-gnu-gcc -pthread -shared -Wl,-O1 -L. -L/scratch/mmokrejs/gentoo/lib -L/scratch/mmokrejs/gentoo/usr/lib -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -O2 -pipe -O2 -pipe -march=native -fwrapv build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/_decimal.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/basearith.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/constants.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/context.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/convolute.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/crt.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/difradix2.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/fnt.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/fourstep.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/io.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/memory.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/mpdecimal.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/numbertheory.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/sixstep.o build/temp.linux-x86_64-3.5/scratch/mmokrejs/gentoo/var/tmp/portage/dev-lang/python-3.5.1-r3/work/Python-3.5.1/Modules/_decimal/libmpdec/transpose.o -L. -L/scratch/mmokrejs/gentoo/lib -L/scratch/mmokrejs/gentoo/usr/lib -lpython3.5 -o build/lib.linux-x86_64-3.5/_decimal.cpython-35-x86_64-linux-gnu.so
*** WARNING: renaming "_crypt" since importing it failed: build/lib.linux-x86_64-3.5/_crypt.cpython-35-x86_64-linux-gnu.so: undefined symbol: crypt
*** WARNING: renaming "nis" since importing it failed: build/lib.linux-x86_64-3.5/nis.cpython-35-x86_64-linux-gnu.so: undefined symbol: yp_master

Following modules built successfully but were removed because they could not be imported:
_crypt                nis