ant target polymer-build-production fails

[duncdrum]

OOTB following the readme instructions build-production ant target produces

polymer-build-production:
     [exec] info: [cli.command.build]    Clearing build/ directory...
     [exec] info: [cli.build.build]    (default) Building...
     [exec] info: [cli.build.build]    (default) Build complete!

production-xar:
     [copy] Copying 1 file to /Users/HALmob/Documents/yo-test/ant/pure-el/build/bundled
     [copy] Copying 1 file to /Users/HALmob/Documents/yo-test/ant/pure-el/build/bundled

BUILD FAILED
/Users/HALmob/Documents/yo-test/ant/pure-el/build.xml:53: Warning: Could not find file /Users/HALmob/Documents/yo-test/ant/pure-el/configuration.xml to copy.

There is no configuration.xml in this repo, nor does polymer-cli produce one, any clue what it is and why ant wants it?

Tried with both polymer-2-element and polymer-2-application