USGS SOAP API deprecated

[j08lue]

From the USGS Python client docs:

As of May 15, 2017 the USGS has deprecated their SOAP API. This library has been updated to use their JSON API. As a result most, if not all, responses through this client will have a different structure compared to the older SOAP version.

This is most probably the reason why the error message could not be parsed in #233 (needs to be fixed in the usgs_eros function) - but not the reason for the error.