pybind: avoid spurious "too many values to unpack"

pybind: avoid spurious "too many values to unpack"

When a user passes e.g. an IP address where
they should have passed a <service>.<id>,
the dots were causing us to raise "too many
values to unpack" exceptions instead of
proper complaints about it not being
a valid service name.

Fixes: #10950
Signed-off-by: John Spray <john.spray@redhat.com>