get_station bombs out on response request

[iceseismic]

Using beta-service,

inventory = client.get_stations(station="ALRZ", level="channel") works fine,
but inventory = client.get_stations(station="ALRZ", level="response") completely bombs out with problems with paz

[mabznz]

Ahhh, I've just written that up at:

https://wiki.geonet.org.nz/display/~b.mabbett/Beta+FDSN+Station+Web+Service+Problem+Defintion#BetaFDSNStationWebServiceProblemDefintion-EmptyPolesZerosentitycausesbuginObspy

It's a problem with empty Entities being produced by beta service I believe. First appears for empty PolesZero entity but could be larger problem.

[nbalfour]

To summarise, it appears that the FDSN station webservice is adding empty elements for poles and zeros when they don't exist in the source stationXML. Need to only add elements if they exist. @junghao can you follow up on this, you can talk to @mabznz if you have questions.

[gclitheroe]

should be fixed and deployed

[nbalfour]

@mabznz, can you please test this to confirm the issue is resolved? Thanks

[mabznz]

Can confirm this was an issue with obspy for both python 2 and 3 but is now fixed with change.

#! /usr/bin/python3.5
from obspy.clients.fdsn import Client
client = Client(base_url='http://beta-service.geonet.org.nz/')
inventory = client.get_stations(network="NZ",level="response")

byron@byron-Latitude-E7250:~/obspy$ ./beta_fsdn_stations.py 
Inventory created at 2017-05-24T14:14:25.000000Z
    Created by: Delta

    Sending institution: GeoNet (WEL(GNS_Test))
    Contains:
        Networks (1):
            NZ
        Stations (915):
            NZ.A11...