run tf-2.3 under python-3.8

Author: guschmue

ci_build/azure_pipelines/unit_test.yml

@@ -3,16 +3,26 @@
 stages:
   - stage:
     jobs:
+    - template: 'templates/job_generator.yml'
+      parameters:
+        python_versions: ['3.8']
+        tf_versions: ['2.3.0']
+        onnx_opsets: ['']
+        job:
+          steps:
+          - template: 'unit_test.yml'
+        report_coverage: 'True'
+
     - template: 'templates/job_generator.yml'
       parameters:
         python_versions: ['3.7']
-        tf_versions: ['1.14.0','1.15.2','2.1.0','2.2.0', '2.3.0']
+        tf_versions: ['1.14.0','1.15.2','2.1.0','2.2.0']
         onnx_opsets: ['']
         job:
           steps:
           - template: 'unit_test.yml'
         report_coverage: 'True'
-    
+
     - template: 'templates/job_generator.yml'
       parameters:
         python_versions: [3.6']