[Buildroot] [git commit branch/2022.02.x] support/tests: print failed command and output on assertRunOK error

[Peter Korsgaard]

commit: https://git.buildroot.net/buildroot/commit/?id=005e5fc0eb0f6fff8622bb552c5b350a79977eb1
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/2022.02.x

Currently, when asserting that a command succeeded, we just capture the
return code of the command. If that is not zero, the assertion fails,
but the error message is not very splicit:
    AssertionError: 1 != 0

Replace the error message with an explicit message that dumps the failed
command, the error code, and the resulting output.

Signed-off-by: Yann E. MORIN <yann.morin.1998 at free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
(cherry picked from commit 44161560dd52ebe9a41ee6e5ec8cacb2a9fe48ec)
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
---
 support/testing/infra/basetest.py | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/support/testing/infra/basetest.py b/support/testing/infra/basetest.py
index 96c6848dfc..45bcd4c2e2 100644
--- a/support/testing/infra/basetest.py
+++ b/support/testing/infra/basetest.py
@@ -88,7 +88,12 @@ class BRTest(BRConfigTest):
         super(BRTest, self).tearDown()
 
     # Run the given 'cmd' with a 'timeout' on the target and
-    # assert that the command succeeded
+    # assert that the command succeeded; on error, print the
+    # faulty command and its output
     def assertRunOk(self, cmd, timeout=-1):
-        _, exit_code = self.emulator.run(cmd, timeout)
-        self.assertEqual(exit_code, 0)
+        out, exit_code = self.emulator.run(cmd, timeout)
+        self.assertEqual(
+            exit_code,
+            0,
+            "\nFailed to run: {}\noutput was:\n{}".format(cmd, '  '+'\n  '.join(out))
+        )