Add script to apply a patch from rietveld.

tests/patch_test.py

Index: tests/patch_test.py
diff --git a/tests/patch_test.py b/tests/patch_test.py
index bd8a4c71a1cf8300ec740ddeeca09801d702519b..b76c693d0d938fa26bc7e2557d39e1d628ee40f1 100755
--- a/tests/patch_test.py
+++ b/tests/patch_test.py
@@ -192,6 +192,20 @@ class PatchTest(unittest.TestCase):
     except patch.UnsupportedPatchFormat:
       pass
 
+  def testFilePatchNoDiff(self):
+    try:
+      patch.FilePatchDiff('foo', '', [])
+      self.fail()
+    except patch.UnsupportedPatchFormat:
+      pass
+
+  def testFilePatchNoneDiff(self):
+    try:
+      patch.FilePatchDiff('foo', None, [])
+      self.fail()
+    except patch.UnsupportedPatchFormat:
+      pass
+
   def testFilePatchBadDiffName(self):
     try:
       patch.FilePatchDiff('foo', SVN_PATCH, [])