Very specific learning for the day but if you are trying to run pulumi-with-ansible IAC and in a world of ssh key pain this bypasses the ssh-agent:
Pulumi.yaml
keypath: "~/.ssh/mykey.pem"
main.py
pulumi.export('keypath', config.require("keypath"))
playbook.yml
ansible_ssh_private_key_file: "{{ keypath }}"
Or just add things properly to your ssh-agent (even better, start using the config):
# Set permissions
chmod -R 400 ~/.ssh/mykey.pem # 600 is also fine
# Add keys to ssh-agent
ssh-agent -s
eval `ssh-agent -s`
ssh-add ~/.ssh/mykeyaws.pem
ssh-add ~/.ssh/mykeyazure.pem