Introduce Bandit Security Linter

This patch introduces the bandit security linter as part of the CI tests
run on feedgen.

.travis.yml

@@ -9,7 +9,7 @@ python:
   - 3.8
 
 install:
-  - pip install flake8 python-coveralls coverage liccheck
+  - pip install bandit flake8 python-coveralls coverage liccheck
   - pip install -r requirements.txt
   - python setup.py bdist_wheel
   - pip install dist/feedgen*

Makefile

@@ -51,3 +51,4 @@ publish:
 test:
 	coverage run --source=feedgen -m unittest discover -s tests
 	flake8 $$(find setup.py tests feedgen -name '*.py')
+	bandit -r feedgen