Rails 4.2 console issues - using RAILS_ENV=development - ruby-on-rails-4

Question

trying to run
$ rails c RAILS_ENV=development
1 warning and 1 error are raised which I do not understand
# warning :
config.eager_load is set to nil. Please update your config/environments/*.rb files accordingly:
* development - set it to false
* test - set it to false (unless you use a tool that preloads your test environment)
* production - set it to true
# error
/config/initializers/devise.rb:13:in `+': no implicit conversion of nil into String (TypeError)
However , the config.eager_load is set to false in the development environment
config/environment/development.rb
Rails.application.configure do
config.cache_classes = false
config.eager_load = false
…/…
And looking at the config/initializers/devise.rb ( line 13) I have
config/initializers/devise.rb
Devise.setup do |config|
…/…
(13) config.mailer_sender = 'no-reply#' + Rails.application.secrets.domain_name
…/…
which lead to the config/secrets.yml file
config/secrets.yml
development:
domain_name: example.com
it's quite understandable , as running rails c ( whithout RAILS_ENV) , I get
$ rails c
development environment (Rails 4.2.3)
irb: warn: can't alias context from irb_context.
irb(main):001:0> Rails.application.secrets.domain_name
=> "example.com"
this warning is also cryptic :
irb: warn: can't alias context from irb_context
could not find any info on Google search... but at least it runs in development ....
why this warning and error using RAILS_ENV ? any enlightenment welcome

Answer 1

too bad .. I should HAVE READ the latest 4.2 doc !!!
so I should NOT be using RAILS_ENV at all !!
$ rails console staging
Loading staging environment (Rails 4.2.3)
irb(main):001:0> exit
$ rails console development
Loading development environment (Rails 4.2.3)
irb: warn: can't alias context from irb_context.
irb(main):001:0> exit