Provisioning fails, Ansible failed to complete successfully

[ubuntupunk]

vagrant provision
==> default: Running provisioner: ansible_local...
Vagrant has automatically selected the compatibility mode '2.0'
according to the Ansible version installed (2.10.8).

Alternatively, the compatibility mode can be specified in your Vagrantfile:
https://www.vagrantup.com/docs/provisioning/ansible_common.html#compatibility_mode

    default: Running ansible-galaxy...
cd /vagrant && ansible-galaxy install --role-file='/vagrant/requirements.yml' --roles-path='/vagrant/roles' --force
Starting galaxy role install process
- changing role ansible-i3 from  to unspecified
- extracting ansible-i3 to /vagrant/roles/ansible-i3
- ansible-i3 was installed successfully
- changing role ansible-polybar from  to unspecified
- extracting ansible-polybar to /vagrant/roles/ansible-polybar
- ansible-polybar was installed successfully
- changing role ansible-rofi from  to unspecified
- extracting ansible-rofi to /vagrant/roles/ansible-rofi
- ansible-rofi was installed successfully
- changing role ansible-xfce4-terminal from  to unspecified
- extracting ansible-xfce4-terminal to /vagrant/roles/ansible-xfce4-terminal
- ansible-xfce4-terminal was installed successfully
- changing role ansible-tmux from  to unspecified
- extracting ansible-tmux to /vagrant/roles/ansible-tmux
- ansible-tmux was installed successfully
- changing role ansible-vim from  to unspecified
- extracting ansible-vim to /vagrant/roles/ansible-vim
- ansible-vim was installed successfully
- changing role ansible-xresources from  to unspecified
- extracting ansible-xresources to /vagrant/roles/ansible-xresources
- ansible-xresources was installed successfully
- changing role ansible-zsh from  to unspecified
- extracting ansible-zsh to /vagrant/roles/ansible-zsh
- ansible-zsh was installed successfully
    default: Running ansible-playbook...
cd /vagrant && PYTHONUNBUFFERED=1 ANSIBLE_FORCE_COLOR=true ANSIBLE_ROLES_PATH='/vagrant/roles' ansible-playbook --limit="all" --inventory-file=/tmp/vagrant-ansible/inventory --become -v playbook.yml
No config file found; using defaults

PLAY [all] *********************************************************************
[WARNING]: While constructing a mapping from /vagrant/group_vars/all, line 2,
column 1, found a duplicate dict key (scheme). Using last defined value only.

TASK [Gathering Facts] *********************************************************
[WARNING]: Unhandled error in Python interpreter discovery for host default:
'<' not supported between instances of 'str' and 'int'
ok: [default]
[WARNING]: Platform linux on host default is using the discovered Python
interpreter at /usr/bin/python, but future installation of another Python
interpreter could change the meaning of that path. See https://docs.ansible.com
/ansible/2.10/reference_appendices/interpreter_discovery.html for more
information.

TASK [ansible-xresources : Ensure .Xresources.d exists] ************************
ok: [default] => {"changed": false, "gid": 1000, "group": "vagrant", "mode": "0755", "owner": "vagrant", "path": "/home/vagrant/.Xresources.d", "size": 4096, "state": "directory", "uid": 1000}

TASK [ansible-xresources : Template main .Xresources file] *********************
fatal: [default]: FAILED! => {"changed": false, "msg": "AnsibleUndefinedVariable: 'main_font' is undefined"}

PLAY RECAP *********************************************************************
default                    : ok=2    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0

Ansible failed to complete successfully. Any error output should be
visible above. Please fix these errors and try again.

[ubuntupunk]

There is no i3 session available after running the provisioning.

[pinpox]

In the output above only the role ansible-xresources seems to have been executed. Did you provision the VM previously already?