tests: fix core file message

Prevent crashing on nonexistent VPP binary path class member when creating
testsuite core message.

Type: fix
Fixes: b23ffd7ef2
Signed-off-by: Dmitry Valter <d-valter@yandex-team.ru>
Change-Id: Ib9b3dc8c69317e6561e5404bbdcbf672e417cbcd

test/hook.py

@@ -6,6 +6,7 @@ from subprocess import check_output, CalledProcessError
 
 import scapy.compat
 import framework
+from config import config
 from log import RED, single_line_delim, double_line_delim
 from util import check_core_path, get_core_path
 
@@ -79,7 +80,7 @@ class PollHook(Hook):
 
     def on_crash(self, core_path):
         self.logger.error("Core file present, debug with: gdb %s %s",
-                          self.test.vpp_bin, core_path)
+                          config.vpp, core_path)
         check_core_path(self.logger, core_path)
         self.logger.error("Running `file %s':", core_path)
         try: