From http://projects.theforeman.org/issues/9185#note-3, when the ENC fails to render, the exception message isn't logged:

Failed to generate external nodes for host4.cloud.example.com with

It appears that refactoring in 4f7a4d0ba84f43e3cb0d422d9f5e82b01588f21b changed the logging message to use $ERROR_INFO instead of $!. This variable is only available if the 'English' library is loaded, which it doesn't appear to be.