* Add new Fedora docker images with Python 3.
* Use consistent env var for lookup test.
* Fix testing of virtualenv with Python 3.
* Fix docker_secret tests on Fedora 26.
* Add Python 3 support to Fedora postgresql test.
* Add Python 3 support to Fedora mysql tests.
* Fix uri test server for Python 3 on Fedora.
* Fix iso_extract test for Python 3 on Fedora.
* Add Python 3 support for Fedora to openssl tests.
* Fix dnf group test for Python 3 on Fedora.
* Use force with user deletion in become test.
This change corrects problems reported by the `yamllint` linter.
Since key duplication problems were removed in 4d48711, this commit
mainly fixes trailing spaces and extra empty lines at beginning/end of
files.
