Stack traces broken in git master for me

According to "git bisect", this problem begin with fcc78e5f.

How exciting. To reproduce, run "make check-local" and verify that you see:

./src/test/test-bt-cl assert | python ./src/test/bt_test.py
BAD
./src/test/test-bt-cl crash | python ./src/test/bt_test.py
BAD