make test: print a warning in case a core_pattern contains a filter program

The default config on Ubuntu 16.04.4 desktop results in truncated cores
when running make test which coredumps. Uninstalling the filter program
(apport) makes the corefiles normal size. Print a warning about that fact,
so the others potentially affected didn't have to wonder.

Change-Id: Iba4b0a2765a25100d6e24fd7f4de0e0339efd835
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>

test/util.py

@@ -70,6 +70,21 @@ def ip6_normalize(ip6):
                             socket.inet_pton(socket.AF_INET6, ip6))
 
 
+def check_core_path(logger, core_path):
+    with open("/proc/sys/kernel/core_pattern", "r") as f:
+        corefmt = f.read()
+        if corefmt.startswith("|"):
+            logger.error(
+                "WARNING: redirecting the core dump through a"
+                " filter may result in truncated dumps.")
+            logger.error(
+                "   You may want to check the filter settings"
+                " or uninstall it and edit the"
+                " /proc/sys/kernel/core_pattern accordingly.")
+            logger.error(
+                "   current core pattern is: %s" % corefmt)
+
+
 class NumericConstant(object):
     __metaclass__ = ABCMeta