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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _fetch_app_role_token(vault_url, role_id, secret_id):
 """Get a Vault token, using the RoleID and SecretID"""

        url = _url_joiner(vault_url, 'v1/auth/approle/login')
        resp = requests.post(url, data={'role_id': role_id, 'secret_id': secret_id})
        resp.raise_for_status()
        data = resp.json()
        if data.get('errors'):
            raise VaultException(u'Error fetching Vault token: {}'.format(data['errors']))
        return data['auth']['client_token']