ROR mysql2 "no implicit conversion of Fixnum into String"

When i access local app http://localhost:3000
getting error:

TypeError
no implicit conversion of Fixnum into String

database.yaml

# Ensure the MySQL gem is defined in your Gemfile
#   gem 'mysql2'
#
# And be sure to use new-style password hashing:
#   http://dev.mysql.com/doc/refman/5.0/en/old-client.html
development:
  adapter: mysql2
  encoding: utf8
  database: app_development
  pool: 5
  username: root
  password: 123456
  socket: /tmp/mysql.sock

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  adapter: mysql2
  encoding: utf8
  database: app_test
  pool: 5
  username: root
  password: 123456
  socket: /tmp/mysql.sock

production:
  adapter: mysql2
  encoding: utf8
  database: app_production
  pool: 5
  username: root
  password: 123456
  socket: /tmp/mysql.sock

To fix the error, just put double quote between password:

  pool: 5
  username: root
  password: "123456"
  socket: /tmp/mysql.sock

restart the server and reload the page.