ament_copyright --add-missing gives KeyError: 'copyright_holder'

edit

I get an error running ament_copyright --add-missing:

$ /opt/ros/eloquent/bin/ament_copyright --add-missing "Clyde McQueen" bsd2
Traceback (most recent call last):
  File "/opt/ros/eloquent/bin/ament_copyright", line 11, in <module>
    load_entry_point('ament-copyright==0.8.1', 'console_scripts', 'ament_copyright')()
  File "/opt/ros/eloquent/lib/python3.6/site-packages/ament_copyright/main.py", line 128, in main
    file_descriptors, name, licenses[args.add_missing[1]], args.verbose)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/ament_copyright/main.py", line 221, in add_missing_header
    header = license_.file_header.format(**{'copyright': copyright_})
KeyError: 'copyright_holder'

I see copyright_holderin the template, but I'm not sure how to set it: https://github.com/ament/ament_lint/b...

Perhaps this is a little-used feature, so nobody has noticed this bug? Workaround is easy, I'll just copy/paste the headers.