The file "Misc/valgrind-python.supp" doesn't work on Linux x64, running Python3.5.2, when configured as such:

  --with-pydebug --with-valgrind --without-pymalloc

Running the interpreter

   echo "x = 1; print(x)" | valgrind --tool=memcheck --leak-check=full --track-origins=yes --verbose --log-file=valgrind.log --suppressions=Misc/valgrind-python.supp /path/to/built/python3

Gives the attached valgrind.log file. The tail of this file says:

==22828== 
==22828== LEAK SUMMARY:
==22828==    definitely lost: 0 bytes in 0 blocks
==22828==    indirectly lost: 0 bytes in 0 blocks
==22828==      possibly lost: 298,529 bytes in 690 blocks
==22828==    still reachable: 605,872 bytes in 4,874 blocks
==22828==         suppressed: 0 bytes in 0 blocks
==22828== Reachable blocks (those to which a pointer was found) are not shown.
==22828== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==22828== 
==22828== ERROR SUMMARY: 256 errors from 256 contexts (suppressed: 0 from 0)
==22828== ERROR SUMMARY: 256 errors from 256 contexts (suppressed: 0 from 0)