Thanks to the work in
JENKINS-41397 we can now detect more errors during the initial REST API call to create a pipeline from Git. We should enhance the UI as follows:
1. Error 403 w/ code: INVALID and field: scmConfig.credentialId should present an error message related to the selected credential.
2. Error 400 w/ code: INVALID and field: scmConfig.uri should present an error next to the repository URL field.
3. Error 403 w/ general message about access denied is probably related to using a URL w/ HTTPS protocol instead of Git. May want to display a more generic error message.