Fix GitBackend.checkout

unittests/autoroll_test.py

Index: unittests/autoroll_test.py
diff --git a/unittests/autoroll_test.py b/unittests/autoroll_test.py
index 9c7d8246956291b4513c7e14bf5b43af6dc25857..99c5478acc9b86cc6ab8bc9a9d99fdb751a48388 100755
--- a/unittests/autoroll_test.py
+++ b/unittests/autoroll_test.py
@@ -4,6 +4,7 @@
 # that can be found in the LICENSE file.
 
 import json
+import logging
 import os
 import subprocess
 import sys
@@ -19,14 +20,18 @@ class TestAutoroll(repo_test_util.RepoTest):
     """
     with repo_test_util.in_directory(repo['root']), \
         repo_test_util.temporary_file() as tempfile_path:
-      subprocess.check_output([
-          sys.executable, self._recipe_tool,
-          '--package', os.path.join(
-              repo['root'], 'infra', 'config', 'recipes.cfg'),
-          '--use-bootstrap',
-          'autoroll',
-          '--output-json', tempfile_path
-      ] + list(args), stderr=subprocess.STDOUT)
+      try:
+        subprocess.check_output([
+            sys.executable, self._recipe_tool,
+            '--package', os.path.join(
+                repo['root'], 'infra', 'config', 'recipes.cfg'),
+            '--use-bootstrap',
+            'autoroll',
+            '--output-json', tempfile_path
+        ] + list(args), stderr=subprocess.STDOUT)
+      except subprocess.CalledProcessError as ex:
+        logging.error('Failed subprocess output: %s', ex.output)
+        raise
       with open(tempfile_path) as f:
         return json.load(f)