Make git auto-svn fail if git svn fetch fails.

git_auto_svn.py

Index: git_auto_svn.py
diff --git a/git_auto_svn.py b/git_auto_svn.py
index 0e8f341c7ca616c50cd7e3a75a1f0b3af0981640..46dce4493ed581ccbab603b2718ee5b3ff747ea2 100755
--- a/git_auto_svn.py
+++ b/git_auto_svn.py
@@ -21,7 +21,7 @@ import urlparse
 import subprocess2
 
 from git_common import run as run_git
-from git_common import run_stream as run_git_stream
+from git_common import run_stream_with_retcode as run_git_stream_with_retcode
 from git_common import set_config, root, ROOT
 from git_footers import parse_footers, get_unique, GIT_SVN_ID_PATTERN
 
@@ -93,8 +93,9 @@ def main(argv):
   set_config('svn-remote.svn.fetch',
              '%s:refs/remotes/%s' % (svn_path, upstream))
   print 'Configured metadata, running "git svn fetch". This may take some time.'
-  for line in run_git_stream('svn', 'fetch').xreadlines():
-    print line.strip()
+  with run_git_stream_with_retcode('svn', 'fetch') as stdout:
+    for line in stdout.xreadlines():
+      print line.strip()
   return 0