Add pylint job to Travis CI

Now that our logging statements are unified, and that we have a proper
pylint configuration that can check this, we can add a CI pipeline job
that performs the actual check, making non-conforming PRs fail when
logging messages do not adhere to the required convention.

Signed-off-by: Rodrigo Tobar <rtobar@icrar.org>

.travis.yml

@@ -74,6 +74,15 @@ jobs:
       script:
         - READTHEDOCS=True make -C docs html SPHINXOPTS="-W --keep-going"
 
+    # Run pylint to enforce our (few) rules
+    - name: pylint
+      python: "3.9"
+      before_install:
+      install:
+        - pip install pylint
+      script:
+        - pylint daliuge-common daliuge-translator daliuge-engine
+
 
 # We want to use docker during the tests
 services: