All HTTP responses except 200 are treated as errors

All responses with except those with response code 200 are treated as errors and as a result of that an exception is thrown.

To my knowledge, not all non-200 responses are errors. An example of this is Google Data Protocol. Check http://code.google.com/apis/gdata/docs/2.0/reference.html#Queries and look for HTTP status codes section. A request made to Google's APIs return a successful response by using 200 response code for OK and 201 response code for CREATED.