gitlabform: Setting deploy key in some cases fail with HTTP 400: {"fingerprint":["has already been taken"]}

For further investigation:

* [215/420] Processing: internal_apps/watchdog
+++ Error while processing 'internal_apps/watchdog'
Traceback (most recent call last):
  File "/srv/gitlab_tools/venv/lib64/python3.5/site-packages/gitlabform/gitlabform/core.py", line 211, in process_all
    self.process_deploy_keys(project_and_group, configuration)
  File "/srv/gitlab_tools/venv/lib64/python3.5/site-packages/gitlabform/gitlabform/core.py", line 31, in method_wrapper
    return method(self, project_and_group, configuration)
  File "/srv/gitlab_tools/venv/lib64/python3.5/site-packages/gitlabform/gitlabform/core.py", line 235, in process_deploy_keys
    self.gl.post_deploy_key(project_and_group, configuration['deploy_keys'][deploy_key])
  File "/srv/gitlab_tools/venv/lib64/python3.5/site-packages/gitlabform/gitlab/projects.py", line 40, in post_deploy_key
    self._make_requests_to_api("projects/%s/deploy_keys", pid, 'POST', deploy_key, expected_codes=201)
  File "/srv/gitlab_tools/venv/lib64/python3.5/site-packages/gitlabform/gitlab/core.py", line 47, in _make_requests_to_api
    response = self._make_request_to_api(path_as_format_string, args, method, data, expected_codes)
  File "/srv/gitlab_tools/venv/lib64/python3.5/site-packages/gitlabform/gitlab/core.py", line 83, in _make_request_to_api
    raise e
gitlabform.gitlab.core.UnexpectedResponseException: Request url='https://xxx/api/v3/projects/1144/deploy_keys', method=POST, data='{'key': 'ssh-ed25519 yyyyyyyyyyy build@xxx.com', 'can_push': True, 'title': 'build@xxx.com auto-bump key'}' failed - expected code(s) 201, got code 400 & body: 'b'{"message":{"fingerprint":["has already been taken"]}}''