Improve log message
When the url path are not correctly provided like /1.1/measurement
instead of 1.1
we raise an error like:
File "h5py/_objects.pyx", line 55, in h5py._objects.with_phil.wrapper
File "h5py/h5o.pyx", line 190, in h5py.h5o.open
KeyError: "Unable to open object (object 'instrument' doesn't exist)"
We should try to have something a bit more 'helpful' for the users.