[Piglit] [PATCH 2/2] unittests: make error messages for generator tests better

[Dylan Baker]

This replaces the simple "it failed" message with the actual stderr
output when the test fails.

Signed-off-by: Dylan Baker <dylanx.c.baker at intel.com>
---
 unittests/generators/test_generators.py | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/unittests/generators/test_generators.py b/unittests/generators/test_generators.py
index fd34177..6e93d91 100644
--- a/unittests/generators/test_generators.py
+++ b/unittests/generators/test_generators.py
@@ -78,15 +78,17 @@ def test_generators():
         """Tester function."""
         msg = ''
 
-        try:
-            with open(os.devnull, 'w') as d:
-                rcode = subprocess.check_call(['python', name], stderr=d,
-                                              stdout=d)
-        except subprocess.CalledProcessError as e:
-            msg = "While calling {}:\n{}".format(name, str(e))
-            rcode = e.returncode
-
-        nt.eq_(rcode, 0, msg)
+        with open(os.devnull, 'w') as d:
+            proc = subprocess.Popen(['python', name],
+                                    stderr=subprocess.PIPE,
+                                    stdout=d)
+            _, err = proc.communicate()
+
+        if proc.returncode != 0:
+            err = err.decode('utf-8')
+
+            raise utils.TestFailure(
+                "failed with message:\n {}".format(err))
 
     description = 'generator: {} runs successfully'
 
-- 
2.8.0