Pass code check with pylint=2.4.4 (#1012)

.github/workflows/code-check.yaml

@@ -0,0 +1,22 @@
+
+name: code-check
+
+on: [push, pull_request]
+
+jobs:
+  code-check:
+    name: Mininet Code Check
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set up Python 3.x
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.x
+      - name: Check out Mininet source
+        uses: actions/checkout@v2
+      - name: Install Mininet code check dependencies
+        run: |
+          PYTHON=`which python` util/install.sh -n
+          python -m pip install pylint==2.4.4
+      - name: Run code check
+        run:  make codecheck

.github/workflows/run-tests.yaml

@@ -24,9 +24,6 @@ jobs:
           # This seems too slow unfortunately:
           # sudo apt-get upgrade -y -qq
           PYTHON=`which python` util/install.sh -nv
-      - name: Run code check (skipping for now)
-        run: |
-          bash -c "if [ `lsb_release -rs` == '14.04' ]; then make codecheck; fi"
       - name: Sanity test
         run: |
           export sudo="sudo env PATH=$PATH"