Duplicated key name error for conjunctive license expression

[JonoYang]

aboutcode-toolkit throws this error on this about file because of the conjunctive license expression:

ABOUT file:

about_resource: ansible-2.7.0.tar.gz
attribute: true
checksum_md5: 6a6f2dd82cfed72bc06204c0b0b2901c
checksum_sha1: 6ad044cfc9e7a33f07fee3304f688bacd43631a7
copyright: Copyright (c) Ansible contributors
description: Ansible is a radically simple IT automation platform that makes your
    applications and systems easier to deploy. Avoid writing scripts or custom code
    to deploy and update your applications— automate in a language that approaches
    plain English, using SSH, with no agents to install on remote systems.
download_url: https://files.pythonhosted.org/packages/7c/4f/a1843687642b8e33637e312b9fb17ca7f68be0641131a92d883368dc6d1c/ansible-2.7.0.tar.gz
homepage_url: https://www.ansible.com/
license_expression: gpl-3.0-plus AND other-permissive AND other-copyleft
licenses:
-   file: gpl-3.0-plus.LICENSE
    key: gpl-3.0-plus
    name: GNU General Public License 3.0 or later
-   file: other-copyleft.LICENSE
    key: other-copyleft
    name: Other Copyleft Licenses
-   file: other-permissive.LICENSE
    key: other-permissive
    name: Other Permissive Licenses
name: Ansible
notice_file: ansible-2.7.0.tar.gz.NOTICE
owner: Ansible Project
owner_url: https://github.com/ansible
redistribute: true
track_changes: true
vcs_repository: https://github.com/ansible/ansible
version: 2.7.0

Error:

$ bin/about-code check thirdparty/
Running aboutcode-toolkit version 3.1.1
Checking ABOUT files...
ERROR: infra/ansible-2.7.0.tar.gz.ABOUT: Duplicated key name(s): ['-   file', '-   file']
Found 1 errors.

This is the license expression and list of license file associated with it:

...
license_expression: gpl-3.0-plus AND other-permissive AND other-copyleft
licenses:
-   file: gpl-3.0-plus.LICENSE
    key: gpl-3.0-plus
    name: GNU General Public License 3.0 or later
-   file: other-copyleft.LICENSE
    key: other-copyleft
    name: Other Copyleft Licenses
-   file: other-permissive.LICENSE
    key: other-permissive
    name: Other Permissive Licenses
...

I would expect that the licenses category should be able to have an arbitrary amount of license files under it.

[chinyeungli]

@JonoYang Thanks for the issue.
The "licenses" group was not introduced at version 3.1.1 and hence doesn't know how to due with these "multiple" keys.
You can give it a try with the develop branch and it should work.