add pylint and travis CI configuration

.pylintrc

@@ -0,0 +1,3 @@
+[MASTER]
+disable=missing-docstring,too-few-public-methods,invalid-name,duplicate-code,superfluous-parens,too-many-locals
+max-line-length=120

.travis.yml

@@ -0,0 +1,8 @@
+dist: xenial   # required for Python >= 3.7
+language: python
+python:
+  - "3.7"
+install:
+  - pip install pylint
+# command to run tests
+script: pylint osbuild assemblers/* stages/*