Merge pull request #11385 from angoenka/update_um_image

TOIL: Update Unified worker image
diff --git a/sdks/python/apache_beam/runners/dataflow/internal/apiclient.py b/sdks/python/apache_beam/runners/dataflow/internal/apiclient.py
index 7651c46..73b20bf 100644
--- a/sdks/python/apache_beam/runners/dataflow/internal/apiclient.py
+++ b/sdks/python/apache_beam/runners/dataflow/internal/apiclient.py
@@ -205,7 +205,7 @@
           ) and 'dev' in beam_version.__version__:
         self.debug_options.add_experiment(
             'runner_harness_container_image='
-            'gcr.io/cloud-dataflow/v1beta3/unified-harness:20200402-rc00')
+            'gcr.io/cloud-dataflow/v1beta3/unified-harness:20200409-rc00')
 
       if self.debug_options.lookup_experiment(
           'runner_harness_container_image') or _use_unified_worker(options):