Nir Soffer authored Mar 11, 2019 and Peter Krempa committed Mar 12, 2019

Commit 2b4bd07e (Add check for params, nparams being a dictionary)
changed the way the optional params argument is treated. If
libvirt.virDomain.blockCopy() is called without specifying params,
params is None, and the call will fail with:

    TypeError: block params must be a dictionary

This is wrong as params is defined as kwarg, breaking existing libvirt
users like oVirt. Add a check for Py_None, so we accept either a dict or
None and fail with TypeError with anything else.

Resolves: https://bugzilla.redhat.com/1687114



Signed-off-by: Nir Soffer <nsoffer@redhat.com>