when you runs a PCT without specifying local checkout sources, the PCT takes the source location from a "scm/connection" field of the POM in the plugin info. In such case PCT will fail if...

• Connection info has a mistake (e.g. Custom Tools Plugin). https://github.com/jenkinsci/customtools-plugin/blob/custom-tools-plugin-0.5/pom.xml#L44
• Connection info points to SSH instead of HTTPs. It will pass iff you have a default key in the environment available w/o passwords. E.g. https://github.com/jenkinsci/coverity-plugin/blob/coverity-1.10.0/pom.xml#L83

Affected plugin: Docker, Custom Tools, Coverity