Define and implement specs for bootstrap-os (#4455)

* Add README to bootstrap-os role

* Rework bootstrap-os once more

* Document workarounds for bugs/deficiencies in Ansible modules
* Unify and document role variables
* Remove installation of additional packages and repositories
* Merge Ubuntu and Debian tasks
* Remove pipelining setting from default playbooks
* Fix OpenSUSE not running its required tasks

roles/bootstrap-os/tasks/bootstrap-fedora.yml

@@ -1,22 +1,46 @@
 ---
+# Some Fedora based distros ship without Python installed
+
+- name: Check if this is an atomic host
+  raw: stat /run/ostree-booted
+  register: ostree
+  environment: {}
+  failed_when: false
+  changed_when: false
+  tags:
+    - facts
+
+- name: Store the fact if this is an atomic host
+  set_fact:
+    is_atomic: "{{ ostree.rc == 0 }}"
+  tags:
+    - facts
+
 - name: Check if bootstrap is needed
-  raw: which "{{ item }}"
+  raw: which python
   register: need_bootstrap
   failed_when: false
   changed_when: false
-  with_items:
-    - python
   environment: {}
-  tags: facts
+  tags:
+    - facts
 
+# Fedora's policy as of Fedora 30 is to still install python2 as /usr/bin/python
+# See https://fedoraproject.org/wiki/FinalizingFedoraSwitchtoPython3 for the current status
 - name: Install python on fedora
-  raw: "dnf install --assumeyes --quiet python"
+  raw: "dnf install --assumeyes --quiet python2"
   become: true
   environment: {}
-  when: need_bootstrap.results | map(attribute='rc') | sort | last | bool
+  when:
+    - need_bootstrap.rc != 0
+    - not is_atomic
 
-- name: Install required python packages
-  dnf:
+# libselinux-python is required on SELinux enabled hosts
+# See https://docs.ansible.com/ansible/latest/installation_guide/intro_installation.html#managed-node-requirements
+- name: Install libselinux-python
+  package:
     name: libselinux-python
     state: present
   become: true
+  when:
+    - not is_atomic