I am asking did_you_mean to use Exception#detailed_message to add
"Did you mean?" suggestion instead of overriding #message method.
https://github.com/ruby/did_you_mean/pull/177
Unfortunately, the change will affect Gem::UnknownCommandError, which
excepts did_you_mean to override #message method.
This PR absorbs the change of did_you_mean.
Gem::CommandManager now calls #detailed_message method to get a message
string with "Did you mean?" suggestion from an exception.
https://github.com/rubygems/rubygems/commit/8f104228d3