This seems to happen when running the playbook again to upgrade an instance.
fatal: [********]: FAILED! => {"changed": false, "msg": "Failed to set a new url https://github.com/openwisp/openwisp-wifi-login-pages.git for origin: fatal: unsafe repository ('/opt/openwisp2/wifi-login-pages' is owned by someone else)\nTo add an exception for this directory, call:\n\n\tgit config --global --add safe.directory /opt/openwisp2/wifi-login-pages\n"}
This seems to happen when running the playbook again to upgrade an instance.