Trouble with mysql gem after updating to mysql 8 installation

I recently updated mysql through brew upgrade to the newest version:

$ mysql -V
mysql  Ver 8.0.11 for osx10.13 on x86_64 (Homebrew)

Now my Ruby on Rails mysql connection stopped working.

For compatibility with the production environment I have to use gem 'mysql', '2.8.1' and everything was working perfectly before updating. After updating mysql I get the following error message:

$ rails s
=> Booting WEBrick
=> Rails 3.2.5 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
    SECURITY WARNING: No secret option provided to Rack::Session::Cookie.
    This poses a security threat. It is strongly recommended that you
    provide a secret to prevent exploits that may be possible from crafted
    cookies. This will not be supported in future versions of Rack, and
    future versions will even invalidate your existing user cookies.

    Called from: /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/actionpack-3.2.5/lib/action_dispatch/middleware/session/abstract_store.rb:28:in `initialize'.

Exiting
/Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/mysql_adapter.rb:32:in `mysql_connection': undefined method `init' for Mysql:Class (NoMethodError)
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:309:in `send'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:309:in `new_connection'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:319:in `checkout_new_connection'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:241:in `checkout'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:236:in `loop'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:236:in `checkout'
from /Users/MyAccount/.rvm/rubies/ruby-version/lib/ruby/1.8/monitor.rb:242:in `synchronize'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:233:in `checkout'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:96:in `connection'
from /Users/MyAccount/.rvm/rubies/ruby-version/lib/ruby/1.8/monitor.rb:242:in `synchronize'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:95:in `connection'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:404:in `retrieve_connection'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_specification.rb:168:in `retrieve_connection'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/connection_adapters/abstract/connection_specification.rb:142:in `connection'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/model_schema.rb:308:in `clear_cache!'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activerecord-3.2.5/lib/active_record/railtie.rb:97:in `_callback_before_13'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/callbacks.rb:418:in `_run__1580337521__prepare__4__callbacks'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/callbacks.rb:405:in `send'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/callbacks.rb:405:in `__run_callback'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/callbacks.rb:385:in `_run_prepare_callbacks'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/callbacks.rb:81:in `send'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/callbacks.rb:81:in `run_callbacks'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/actionpack-3.2.5/lib/action_dispatch/middleware/reloader.rb:74:in `prepare!'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/actionpack-3.2.5/lib/action_dispatch/middleware/reloader.rb:48:in `prepare!'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/railties-3.2.5/lib/rails/application/finisher.rb:47
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/railties-3.2.5/lib/rails/initializable.rb:30:in `instance_exec'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/railties-3.2.5/lib/rails/initializable.rb:30:in `run'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/railties-3.2.5/lib/rails/initializable.rb:55:in `run_initializers'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/railties-3.2.5/lib/rails/initializable.rb:54:in `each'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/railties-3.2.5/lib/rails/initializable.rb:54:in `run_initializers'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/railties-3.2.5/lib/rails/application.rb:136:in `initialize!'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/railties-3.2.5/lib/rails/railtie/configurable.rb:30:in `send'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/railties-3.2.5/lib/rails/railtie/configurable.rb:30:in `method_missing'
from /Users/MyAccount/Development/REPRO/webapp/config/environment.rb:9
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/dependencies.rb:251:in `gem_original_require'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/dependencies.rb:251:in `require'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/dependencies.rb:251:in `require'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/dependencies.rb:236:in `load_dependency'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/activesupport-3.2.5/lib/active_support/dependencies.rb:251:in `require'
from /Users/MyAccount/Development/REPRO/webapp/config.ru:3
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/rack-1.4.7/lib/rack/builder.rb:51:in `instance_eval'
from /Users/MyAccount/.rvm/gems/ruby-version@webapp/gems/rack-1.4.7/lib/rack/builder.rb:51:in `initialize'
from /Users/MyAccount/Development/REPRO/webapp/config.ru:0:in `new'
from /Users/MyAccount/Development/REPRO/webapp/config.ru:0

How can I solve this problem? Is there a way to solve the mysql connection?

Unfortunately mysql2 is not an option for the production environment.