Required files
rubygems/rubygems_version
rubygems/defaults
thread
rbconfig
fileutils
sources
rubygems/config_file
rbconfig/datadir
rubygems/exceptions
rubygems/version
rubygems/requirement
rubygems/dependency
rubygems/gem_path_searcher
rubygems/source_index
rubygems/platform
rubygems/builder
rubygems/custom_require