unittests: handle some renamed assert methods

Python 3 renamed assert{ItemsEqual,RaisesRegexp,RegexpMatches} to
assert{CountEqual,RaisesRegex,Regex}.  Add our own handlers so we
can migrate our code now.

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

Change-Id: I21cd4ce0b8ec6757422028d0228fea9e91cb2b1c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1829816
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/api/controller/packages_unittest.py b/api/controller/packages_unittest.py
index 98f562c..58fe3d1 100644
--- a/api/controller/packages_unittest.py
+++ b/api/controller/packages_unittest.py
@@ -80,7 +80,7 @@
                                         output_dir)
     # First argument (build targets) of the first (only) call.
     call_targets = uprev_patch.call_args[0][0]
-    self.assertItemsEqual(targets, [t.name for t in call_targets])
+    self.assertCountEqual(targets, [t.name for t in call_targets])
 
     for ebuild in self.response.modified_ebuilds:
       self.assertIn(ebuild.path, changed)
@@ -164,7 +164,7 @@
 
     for idx, uprev_response in enumerate(self.response.responses):
       self.assertEqual(result.modified[idx].new_version, uprev_response.version)
-      self.assertItemsEqual(
+      self.assertCountEqual(
           result.modified[idx].files,
           [ebuild.path for ebuild in uprev_response.modified_ebuilds])