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##### SUMMARY
<!--- Explain the problem briefly below -->

`python-gitlab` library release a new version [v1.13.0](https://github.com/python-gitlab/python-gitlab/releases/tag/v1.13.0). User/Password authentication as been removed completely causing all Ansible GitLab module to fail... 

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->

gitlab_group
gitlab_deploy_key
gitlab_hook
gitlab_project
gitlab_project_variable
gitlab_runner
gitlab_user

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
All versions

this_gitlab.delete_variable(key)
                change = True
                return_value['removed'].append(key)
        elif key not in existing_variables and state == 'present':
            this_gitlab.create_variable(key, var_list[key])
            change = True
            return_value['added'].append(key)
    existing_variables = list(filter(None, existing_variables))
    if purge:
        for item in existing_variables:
            this_gitlab.delete_variable(item)
            change = True
            return_value['removed'].append(item)
    else:
        return_value['untouched'].extend(existing_variables)
    return change, return_value
def main():
    argument_spec = basic_auth_argument_spec()
    argument_spec.update(
        api_token=dict(type='str', required=True, no_log=True),
        project=dict(type='str', required=True),
        purge=dict(type='bool', required=False, default=False),
        vars=dict(type='dict', required=False, default=dict()),
        state=dict(type='str', default="present", choices=["absent", "present"])
    )
    module = AnsibleModule(
        argument_spec=argument_spec,
        mutually_exclusive=[
            ['api_username', 'api_token'],
            ['api_password', 'api_token'],