Support for the Ruby 2.4 series has ended. See here for reference.
SilentUI is a UI choice that is absolutely silent.
The SilentUI has no arguments as it does not use any stream.
# File rubygems/user_interaction.rb, line 681
def initialize
reader, writer = nil, nil
reader = File.open(Gem::Util::NULL_DEVICE, 'r')
writer = File.open(Gem::Util::NULL_DEVICE, 'w')
super reader, writer, writer, false
end