[FATAL] Ansible Release 12.0 Breaks netlab Jinja2 Templates
On September 9th, the ansible release 12.0 appeared on PyPi. It requires ansible-core release 2.19, which includes breaking changes to Jinja2 templating. netlab Jinja2 templates rely on a few Ansible Jinja2 filters; netlab thus imports and uses those filters, and it looks like those imports pulled in the breaking changes that consequently broke the netlab containerlab configuration file template (details).
netlab did not check the Ansible core version (we never had a similar problem in the past), and the installation scripts did not pin the Ansible version (feel free to blame me for this one), which means that any new netlab installation created after September 9th crashed miserably on the simplest lab topologies.
This is the workaround we implemented in netlab release 25.09-post1 (released earlier today):


