[PATCH net-next] selftests: net: add more info to error in bpf_offload

[Jakub Kicinski <kuba@kernel.org>]

bpf_offload caught a spurious warning in TC recently, but the error
message did not provide enough information to know what the problem
is:

  FAIL: Found 'netdevsim' in command output, leaky extack?

Add the extack to the output:

  FAIL: Unexpected command output, leaky extack? ('netdevsim', 'Warning: Filter with specified priority/protocol not found.')

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 tools/testing/selftests/net/bpf_offload.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/bpf_offload.py b/tools/testing/selftests/net/bpf_offload.py
index 3efe44f6e92a..d10f420e4ef6 100755
--- a/tools/testing/selftests/net/bpf_offload.py
+++ b/tools/testing/selftests/net/bpf_offload.py
@@ -594,8 +594,9 @@ def bpftool_prog_load(sample, file_name, maps=[], prog_type="xdp", dev=None,
     check_extack(output, "netdevsim: " + reference, args)
 
 def check_no_extack(res, needle):
-    fail((res[1] + res[2]).count(needle) or (res[1] + res[2]).count("Warning:"),
-         "Found '%s' in command output, leaky extack?" % (needle))
+    haystack = (res[1] + res[2]).strip()
+    fail(haystack.count(needle) or haystack.count("Warning:"),
+         "Unexpected command output, leaky extack? ('%s', '%s')" % (needle, haystack))
 
 def check_verifier_log(output, reference):
     lines = output.split("\n")
-- 
2.47.0