invokeAPI() --> ApiException() if non HTTP 200

There was no error indication in case the restapi request gets back a non HTTP 200 code, e.g. HTTP 400 / 401 / 403 / ....

Author: psytester

src/main/java/com/docusign/esign/client/ApiClient.java

@@ -22,6 +22,7 @@
 import org.apache.oltu.oauth2.client.request.OAuthClientRequest.TokenRequestBuilder;
 import org.apache.oltu.oauth2.common.exception.OAuthSystemException;
 
+import javax.ws.rs.core.Response.Status;
 import javax.ws.rs.core.Response.Status.Family;
 import javax.ws.rs.core.UriBuilder;
 import javax.ws.rs.core.MediaType;
@@ -746,6 +747,10 @@ public <T> T invokeAPI(String path, String method, List<Pair> queryParams, Objec
 
     ClientResponse response = getAPIResponse(path, method, queryParams, body, headerParams, formParams, accept, contentType, authNames);
 
+    if (response.getStatusInfo().getStatusCode() != Status.OK.getStatusCode()) {
+        throw new ApiException("Error while requesting server, received HTTP code: "+ response.getStatusInfo().getStatusCode() + " / with response Body: " + response.getEntity(String.class));
+    }
+
     statusCode = response.getStatusInfo().getStatusCode();
     responseHeaders = response.getHeaders();