[IMP] Add option to make isolated pylint

As commented on #126
Here is a more compact alternative:

    # Test list. Each test is a list with command + arguments.
    tests = []
    if os.environ.get("LINT_CHECK", "1") == "1":
        tests.append(['test_server'])
    # By default, do lint checks
    if os.environ.get("LINT_CHECK", "1") == "1":
        tests.append(['test_flake8'])
        tests.append(['test_pylint'])
    exit(main(tests))