Have you tried this ssl_mode: 'DISABLED'?

johndoe_dev: &johndoe_dev
  adapter: mysql2
  database: the_wagon
  pool: 25
  socket: /tmp/mysql.sock
  host: localhost
  timeout: 5000
  username: myuser
  password: password
  encoding: utf8mb4
  collation: utf8mb4_unicode_ci
  variables:
    sql_mode: TRADITIONAL
  ssl_mode: 'DISABLED' 

development:
  <<: *johndoe_dev