<!--- Verify first that your issue is not already reported on GitHub -->
<!--- Also test if the latest release and devel branch are affected too -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### 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

name: My Name
    username: myusername
    password: mysecretpassword
    email: me@example.com
    sshkey_name: MySSH
    sshkey_file: ssh-rsa AAAAB3NzaC1yc...
    state: present
    group: super_group/mon_group
    access_level: owner
  delegate_to: localhost
'''
RETURN = '''
msg:
  description: Success or failure message
  returned: always
  type: str
  sample: "Success"
result:
  description: json parsed response from the server
  returned: always
  type: dict
error:
  description: the error message returned by the GitLab API
  returned: failed
  type: str
  sample: "400: path is already in use"
user:
  description: API object
  returned: always
  type: dict