Service valid check is not accurate

[jw3]

The service valid check always reports true. The problem is that valid is based on the active state, assuming it errors if the service does not exist. Instead the active check returns inactive if it doesnt exist, the lack of error results in a valid state.

Example: This should (on most systems) print True, False, currently prints True, True

print(Handle("sshd").is_valid())
print(Handle("a_service_that_does_not_exist").is_valid())