3rd circleci run

.circleci/config.yml

           command: |
             . venv/bin/activate
             pre-commit run --hook-stage manual markdown-link-check --all-files
-  
+
   protobuf_generation_check:
     docker:
       - image: circleci/python:3.7.3
           executor: python373
           pyversion: 3.7.3
           # Test python 3.7 with the newest supported versions
-          pip_constraints: test_constraints_max_version.txt
+          pip_constraints: test_constraints_max_tf1_version.txt
+      - build_python:
+          name: python_3.7.3+tf2
+          executor: python373
+          pyversion: 3.7.3
+          # Test python 3.7 with the newest supported versions
+          pip_constraints: test_constraints_max_tf2_version.txt
       - markdown_link_check
       - protobuf_generation_check

test_constraints_max_tf2_version.txt

 # pip constraints to use the *highest* versions allowed in ml-agents/setup.py
+# tensorflow >= 2.0
 # For projects with upper bounds, we should periodically update this list to the latest release version
 grpcio>=1.23.0
 numpy>=1.17.2

test_constraints_max_tf1_version.txt

+# pip constraints to use the *highest* versions allowed in ml-agents/setup.py
+# with the exception of tensorflow, which is constrained to <2
+# For projects with upper bounds, we should periodically update this list to the latest release version
+grpcio>=1.23.0
+numpy>=1.17.2
+tensorflow>=1.14.0,<2.0