«Beginners Guide to Install Discourse on Ubuntu for Development».
I use the latest stock version of Ubuntu Desktop (16.04.3 LTS) which is unmodified, without any extra packages previously installed apart from the guide’s previous steps packages .
The bundle exec rake autospec guide’s step fails:
~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-support-3.6.0/lib/rspec/support.rb:28:in `require_relative': cannot load such file -- ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-support-3.6.0/lib/rspec/support/source (LoadError) from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-support-3.6.0/lib/rspec/support.rb:28:in `block in <module:Support>' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-support-3.6.0/lib/rspec/support.rb:19:in `block in define_optimized_require_for_rspec' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/world.rb:135:in `source_from_file' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/snippet_extractor.rb:18:in `source_from_file' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/snippet_extractor.rb:30:in `extract_expression_lines_at' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/exception_presenter.rb:218:in `read_failed_lines' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/exception_presenter.rb:163:in `failure_slash_error_lines' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/exception_presenter.rb:150:in `block in failure_lines' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/exception_presenter.rb:149:in `tap' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/exception_presenter.rb:149:in `failure_lines' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/exception_presenter.rb:34:in `colorized_message_lines' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/exception_presenter.rb:240:in `formatted_message_and_backtrace' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/exception_presenter.rb:86:in `fully_formatted_lines' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/exception_presenter.rb:78:in `fully_formatted' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/notifications.rb:200:in `fully_formatted' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/notifications.rb:114:in `block in fully_formatted_failed_examples' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/notifications.rb:113:in `each' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/notifications.rb:113:in `each_with_index' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/notifications.rb:113:in `fully_formatted_failed_examples' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/formatters/base_text_formatter.rb:32:in `dump_failures' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/reporter.rb:206:in `block in notify' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/reporter.rb:205:in `each' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/reporter.rb:205:in `notify' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/reporter.rb:175:in `block in finish' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/reporter.rb:191:in `close_after' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/reporter.rb:171:in `finish' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/reporter.rb:81:in `ensure in report' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/reporter.rb:81:in `report' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:112:in `run_specs' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:87:in `run' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:71:in `run' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:45:in `invoke' from ~/.rbenv/versions/2.4.2/lib/ruby/gems/2.4.0/gems/rspec-core-3.6.0/exe/rspec:4:in `<top (required)>' from bin/rspec:16:in `load' from bin/rspec:16:in `<main>' 
A similar problem: meta.discourse.org/t/topic/69830