Development database fixtures failing due to missing RSpec dependency

Summary

When running gdk install as of (at least) GDK 3c9832c5ca, you can encounter this NoMethodError: undefined method configure' for RSpec:Module`:

== Seed from /Users/djensen/Code/gitlab-development-kit/gitlab/db/fixtures/development/01_admin.rb
**************************************************
⛔️ WARNING: Sidekiq testing API enabled, but this is not the test environment.  Your jobs will not go to Redis.
**************************************************
rake aborted!
NoMethodError: undefined method `configure' for RSpec:Module
/Users/djensen/Code/gitlab-development-kit/gitlab/spec/support/sidekiq.rb:29:in `<main>'
(eval):1:in `block (2 levels) in run_file'
/Users/djensen/Code/gitlab-development-kit/gitlab/lib/tasks/gitlab/setup.rake:34:in `setup_db'
/Users/djensen/Code/gitlab-development-kit/gitlab/lib/tasks/gitlab/setup.rake:5:in `block (2 levels) in <main>'
/Users/djensen/Code/gitlab-development-kit/gitlab/lib/tasks/dev.rake:7:in `block (2 levels) in <main>'
/Users/djensen/.rbenv/versions/2.6.3/bin/bundle:23:in `load'
/Users/djensen/.rbenv/versions/2.6.3/bin/bundle:23:in `<main>'
Tasks: TOP => db:seed_fu
(See full trace by running task with --trace)
support/bootstrap-rails failed
make: *** [postgresql/data] Error 1

Specifically, the problem is that many of the fixture files require spec/support/sidekiq.rb without first loading rspec/core (where the configure method is defined).

Steps to reproduce

Follow the Set up GDK instructions

What is the current bug behavior?

There is a NoMethodError when trying to run the db/fixtures/development files (at least in the GDK context).

What is the expected correct behavior?

The db/fixtures/development files can be run successfully.

Possible fixes

I think this can be fixed by either:

• reverting the recent change that created this bug (what was this?)
• or adding require 'rspec/rails' as the first line of spec/support/sidekiq.rb
• or adding require 'rspec/rails' as the first line in the 16 files in db/fixtures/development that require './spec/support/sidekiq'

Note require 'rspec/core' results in "LoadError: cannot load such file -- rspec-core".