Another simpler attempt to fix travis build (#13257)

* Remove usage of method deleted in latest jackson-databind

* Revert "Remove usage of method deleted in latest jackson-databind"

This reverts commit 81cb5d41d9.

* Use get-pip to install pip

* Use default pyyaml version

* Upgrade pyyaml

.travis.yml

@@ -91,10 +91,11 @@ jobs:
 
     - name: "license checks"
       before_script: &setup_generate_license
-        - sudo apt-get update && sudo apt-get install python3 python3-pip python3-setuptools -y
+        - sudo apt-get update && sudo apt-get install python3 -y
+        - curl https://bootstrap.pypa.io/pip/3.5/get-pip.py | sudo -H python3
         - ./check_test_suite.py && travis_terminate 0 || echo 'Continuing setup'
         - pip3 install wheel  # install wheel first explicitly
-        - pip3 install pyyaml==5.4.1
+        - pip3 install --upgrade pyyaml
       script:
         - >
           ${MVN} apache-rat:check -Prat --fail-at-end