Whether or not debug
messages should be printed. By default, whether or not the
`MOLINILLO_DEBUG` environment variable is set.
@return [Boolean]
# File lib/rubygems/resolver/molinillo/lib/molinillo/modules/ui.rb, line 60
def debug?
return @debug_mode if defined?(@debug_mode)
@debug_mode = ENV['MOLINILLO_DEBUG']
end