targetHost accepts only IP

[prekageo]

The targetHost argument accepts only IP. If I give a hostname, I don't get an error message. Instead I see:

Will start load for 10000 samples with 20.0 sampling rate
Will start load for 10000 samples with 20.0 sampling rate
No tx samples
No tx samples
There are 0 samples
/tmp/XXX/lancet/venv/lib/python3.7/site-packages/numpy/core/fromnumeric.py:3257: RuntimeWarning: Mean of empty slice.
  out=out, **kwargs)
/tmp/XXX/lancet/venv/lib/python3.7/site-packages/numpy/core/_methods.py:161: RuntimeWarning: invalid value encountered in double_scalars
  ret = ret.dtype.type(ret / rcount)
Traceback (most recent call last):
  File "/tmp/XXX/lancet/venv/bin/lancet", line 10, in <module>
    sys.exit(main())
  File "/tmp/XXX/lancet/venv/lib/python3.7/site-packages/manager/lancet.py", line 117, in main
    server.run(args=args)
  File "/tmp/XXX/lancet/venv/lib/python3.7/site-packages/manager/lancet.py", line 79, in run
    res = self.process_msg(msg)
  File "/tmp/XXX/lancet/venv/lib/python3.7/site-packages/manager/lancet.py", line 103, in process_msg
    self.controller.get_per_thread_samples())
  File "/tmp/XXX/lancet/venv/lib/python3.7/site-packages/manager/stats.py", line 142, in aggregate_latency
    agg.Avg_latency = int(numpy.mean(all_samples))
ValueError: cannot convert float NaN to integer
Error getting latency replies: Read from agent failed: EOF

I think it would be more user-friendly, if an appropriate error message is returned when the agents can't connect to the target host.