'hanna --gems' exception with uninitialized constant Gem::UserInteraction

[trevor]

also hanna --gems is listed on the readme, but not in hanna --help

% hanna --gems rails
/usr/local/Cellar/ruby/1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems/doc_manager.rb:14:in `<class:DocManager>': uninitialized constant Gem::UserInteraction (NameError)
    from /usr/local/Cellar/ruby/1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems/doc_manager.rb:12:in `<top (required)>'
    from /usr/local/Cellar/ruby/1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:55:in `require'
    from /usr/local/Cellar/ruby/1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:55:in `require'
    from /usr/local/Cellar/ruby/1.9.2-p180/lib/ruby/gems/1.9.1/gems/hanna-0.1.12/bin/hanna:48:in `<top (required)>'
    from /usr/local/Cellar/ruby/1.9.2-p180/bin/hanna:19:in `load'
    from /usr/local/Cellar/ruby/1.9.2-p180/bin/hanna:19:in `<main>'

% cat ~/.gemrc
gem: --no-ri
rdoc: --inline-source --line-numbers --fmt=html --template=hanna

% gem -v                            
1.8.5

% gem list -l hanna  

*** LOCAL GEMS ***

hanna (0.1.12)

% ruby -v
ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-darwin10.7.0]

% rdoc --version
rdoc 3.8