handle authentication errors on gnd api
the SUB is authorized to access http://services.dnb.de/sru/authorities. Outside the SUB (campus?) network a request like http://services.dnb.de/sru/authorities?operation=searchRetrieve&version=1.1&query=dnb.per%3Dringeln*%20and%20BBG%3DTp*&recordSchema=RDFxml&maximumRecords=50 are responded with an error like
<searchRetrieveResponse>
<version>1.1</version>
<diagnostics>
<diag:diagnostic>
<diag:uri>info:srw/diagnostic/1/3</diag:uri>
<diag:details>Authentication error</diag:details>
<diag:message>No Account for IpAddress: 89.175.12.34</diag:message>
</diag:diagnostic>
</diagnostics>
</searchRetrieveResponse>
this should be handled by the api to respond with an appropriate error message. also unit tests will fail when executed outside the campus. this can't be handled by %test:assumeIntenetAccess($uri) as the server is reachable and responding.