unittests: change self.assertEquals to self.assertEqual

The unittest module has deprecated the former name.

BUG=chromium:980619
TEST=`cros lint` is unchanged

Change-Id: I2b93cc6079d1bf49950ec0cdef7a4edcdf5535ed
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1810597
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/pushimage_unittest.py b/scripts/pushimage_unittest.py
index e5e35b7..e17fd6f 100644
--- a/scripts/pushimage_unittest.py
+++ b/scripts/pushimage_unittest.py
@@ -186,7 +186,7 @@
     """Verify diff priority values get used correctly"""
     for prio, sprio in ((0, '00'), (9, '09'), (35, '35'), (99, '99')):
       ret = pushimage.MarkImageToBeSigned(self.ctx, '', '', prio)
-      self.assertEquals(ret, '/tobesigned/%s,' % sprio)
+      self.assertEqual(ret, '/tobesigned/%s,' % sprio)
 
   def testBadPriority(self):
     """Verify we reject bad priority values"""