make test: improve debugability

Introduce faulthandler to print stack trace to stderr on python crash.
Don't disable automatic garbage collection to decrease the chances of
running out of memory.

Change-Id: I6927a5f6ea9569735d084d4ed3d258950a400d74
Signed-off-by: Klement Sekera <ksekera@cisco.com>
diff --git a/test/Makefile b/test/Makefile
index 8df9640..14c8cd2 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -35,7 +35,7 @@
 endif
 
 PYTHON_VENV_PATH=$(VPP_PYTHON_PREFIX)/virtualenv
-PYTHON_DEPENDS=six scapy==2.3.3 pexpect subprocess32 cffi git+https://github.com/klement/py-lispnetworking@setup
+PYTHON_DEPENDS=faulthandler six scapy==2.3.3 pexpect subprocess32 cffi git+https://github.com/klement/py-lispnetworking@setup
 SCAPY_SOURCE=$(shell find $(PYTHON_VENV_PATH) -name site-packages)
 BUILD_COV_DIR=$(BR)/test-cov