Check_MK Werk 7325: check_bi_aggr: Improve GUI application error handling

ID: 7325 Title: check_bi_aggr: Improve GUI application error handling Component: Checks & agents Level: 1 Class: Bug fix Version: 1.6.0i1 When the webservice detects an error -- such as an authentication problem -- it does not output the expected data structure, but a string starting with "ERROR:". This is now correctly being detected and the error is output as check output, rather than a nasty parsing exception.