roll_deps: Return a tuple even when returning early

This fixes the bot going red when DEPS is already up-to-date.

BUG=skia:
R=halcanary@google.com

Author: borenet@google.com

Review URL: https://codereview.chromium.org/185413012

git-svn-id: http://skia.googlecode.com/svn/trunk@13642 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tools/roll_deps.py b/tools/roll_deps.py
index 6ee37c3..ebecad3 100755
--- a/tools/roll_deps.py
+++ b/tools/roll_deps.py
@@ -416,7 +416,7 @@
         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 @@
 
     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):