Comment 4 for bug 1626334

Without digging deeper, my intuition tells me that this could be one of of a few things:

(1) The version of python-pyvmomi we have in the repository may be too old to talk to this server. In that case, the following *might* work around the issue (though you would be getting into 'unsupported' territory):

    sudo pip3 install --system --upgrade pyvmomi

(2) It could be an issue with the power parameters. For historical reasons (I think), ports cannot be specified as "host[:port]" in the many of the power drivers. Make sure you are using the 'port' field to enter the port number.

(3) If you do (1) and (2) and it still doesn't work, it might be an issue with the certificate. Newer versions of the python-pyvmomi API will verify the server certificate, which can be inconvenient. In that case, first make sure you have the latest version of MAAS (from the stable PPA), and then either make sure your system considers the certificate trusted (and make sure the certificate's subnet matches the VMware server hostname), or change the power parameters to use protocol=https+unverified.

Hope that helps. Please let me know if any of the above solves your issue.