Set proxy option in early dnf invocation

If hosts need to use a proxy to install packages and python is absent,
the call to install the python package will hang, at least on CentOS.

Set proxy if it exists in dnf_config using a command-line option. Later
uses of dnf will be after dnf.conf has been updated.

Change-Id: Ic949577afd3ea07306cebf224637a08a1ecce0f5
Story: 2009274
Task: 43528

ansible/kayobe-ansible-user.yml

@@ -40,6 +40,9 @@
   gather_facts: no
   vars:
     ansible_user: "{{ bootstrap_user }}"
+    dnf_options:
+      - "-y"
+      - "{% if 'proxy' in dnf_config %}--setopt=proxy={{ dnf_config['proxy'] }}{% endif %}"
   tags:
     - ensure-python
   tasks:
@@ -49,8 +52,9 @@
       failed_when: false
       register: check_python
 
+    # TODO(priteau): Support apt proxy
     - name: Ensure python is installed
-      raw: test -e /usr/bin/apt && (sudo apt -y update && sudo apt install -y python3-minimal) || (sudo dnf -y install python3)
+      raw: "test -e /usr/bin/apt && (sudo apt -y update && sudo apt install -y python3-minimal) || (sudo dnf {{ dnf_options | select | join(' ') }} install python3)"
       when: check_python.rc != 0
 
 - name: Ensure the Kayobe Ansible user account exists

releasenotes/notes/dnf-proxy-22a6eb457c06a223.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Sets proxy option when using ``dnf`` during user bootstrapping, before
+    ``dnf.conf`` is updated. This allows Kayobe to install Python 3 during host
+    configuration when ``dnf`` requires a proxy to operate.