default: &default
    configCache: false
    tmpdir: {API_PROJECT_DIR}tmp/

    hosts:
        example.org:



---
PyYAML says:
expected <block end>, but found '<scalar>'
  in "<string>", line 4, column 30:
        tmpdir: {API_PROJECT_DIR}tmp/
                                 ^

---
default: &default
    configCache: false
    tmpdir: '{API_PROJECT_DIR}tmp/'

    hosts:
        example.org:

---
default: &default
    configCache: false
    tmpdir: |-
      {API_PROJECT_DIR}tmp/

    hosts:
        example.org: