Syntax Error while loading YAML - did not find expected key

Olá,

Quando executo o YML abaixo:

- hosts: all
  tasks:
    - name: 'Instala pacotes do sistema operacional'
      apt:
        name:
        - php5
        - apache2
        - libapache2-mod-php5
        - php5-gd
        - libssh2-php
        - php5-mcrypt
        - mysql-server-5.6
        - python-mysqldb
        - php5-mysql
        state: latest
      become: yes

    - name: Create mysql database - wordpress_db
          mysql_db:
            name: wordpress_db
            state: present 
          become: yes

Esta retornando o seguinte erro:

ERROR! We were unable to read either as JSON nor YAML, these are the errors we got from each:
JSON: No JSON object could be decoded

Syntax Error while loading YAML.
  did not find expected key

The error appears to be in '/home/elder/ambiente-dev2/wordpress_com_ansible/provisioning.yml': line 19, column 7, but may
be elsewhere in the file depending on the exact syntax problem.

The offending line appears to be:


      - name: Create mysql database - wordpress_db
      ^ here

Dei uma lida nos outros fóruns e até encontrei erros parecidos, mas não entendi o que ainda estou fazendo de errado. Poderiam me ajudar por favor?