运行时：$rails new app 我得到一个错误！（最近更新的红宝石。）
macOS Mojave 10.14.6
rails -v = ruby 2.6.3p62 (2019-04-16 revision 67580) [x86_64-darwin18]
运行时：$rails new app
/Users/.rbenv/versions/2.3.0/lib/ruby/2.3.0/rubygems/dependency.rb:319:in to_specs': Could not find 'railties' (>= 0.a) among 14 total gem(s) (Gem::LoadError)
签入 ' GEM_PATH=/Users/.rvm/gems/ruby-2.6.3:/Users/.rvm/gems/ruby-2.6.3@global'，执行gem env以获取更多信息
from/Users/.rbenv/versions/2.3.0/lib/ruby/2.3.0/rubygems/dependency.rb:328:in to_spec'
from/Users/.rbenv/versions/2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_gem.rb:65:in `gem'
from/Users/.rbenv/versions/2.3.0/bin/rails:22:in `<main>'
任何与 Rails 相关的代码都不起作用。