roll_deps: Return a tuple even when returning early

tools/roll_deps.py

Index: tools/roll_deps.py
diff --git a/tools/roll_deps.py b/tools/roll_deps.py
index 6ee37c32b8d2c41ae1a304d277a0f1b75fd142e3..ebecad3396f6883f297c2e91c57ae0e5e7fecb63 100755
--- a/tools/roll_deps.py
+++ b/tools/roll_deps.py
@@ -416,7 +416,7 @@ def roll_deps(config, revision, git_hash):
         assert old_revision
         if revision == int(old_revision):
             print 'DEPS is up to date!'
-            return None
+            return (None, None)
 
         master_hash = config.vsp.strip_output(
             [git, 'show-ref', 'origin/master', '--hash'])
@@ -506,12 +506,13 @@ def find_hash_and_roll_deps(config, revision=None, partial_hash=None):
 
     print 'revision=%r\nhash=%r\n' % (revision, git_hash)
 
-    roll = roll_deps(config, revision, git_hash)
+    deps_issue, whitespace_issue = roll_deps(config, revision, git_hash)
 
-    if roll:
-        deps_issue, whitespace_issue = roll
+    if deps_issue and whitespace_issue:
         print 'DEPS roll:\n    %s\n' % deps_issue
         print 'Whitespace change:\n    %s\n' % whitespace_issue
+    else:
+        print >> sys.stderr, 'No issues created.'
 
 
 def main(args):