python/tests/blackbox: check_exit_code() explains by default

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

diff --git a/python/samba/tests/__init__.py b/python/samba/tests/__init__.py
index 2eaf9785a1d03f2dcf1b6e71e0a60b246d9b77d5..e95b6a9157af8bdc38f68c4ba5dea583d2a5229b 100644 (file)
--- a/python/samba/tests/__init__.py
+++ b/python/samba/tests/__init__.py
@@ -413,6 +413,8 @@ class BlackboxTestCase(TestCaseInTempDir):
         stdoutdata, stderrdata = p.communicate()
         retcode = p.returncode
         if retcode != expected:
+            if msg is None:
+                msg = "expected return code %s; got %s" % (expected, retcode)
             raise BlackboxProcessError(retcode,
                                        line,
                                        stdoutdata,