VERIFIED SOLUTION i
Error 'CustomLicenseValidationAction.install(): cert.pem does not exist ' is observed while installing EngageOne Deliver (formerly e-Messaging and EngageOne Digital Delivery) on non Windows platform.
This may be caused if 'cert.pem' file is not present in the 'unix' directory of the EngageOne Deliver installer.
ResolutionUPDATED: May 27, 2019
'cert.pem' file is a part of EngageOne Deliver installer. To install EngageOne Deliver, it is mandatory to have the 'cert.pem' in the 'unix' directory. If cert.pem' does not exist in the 'unix' directory, installer has not been downloaded completely.