Fix #136 parse error with 500 response for project delete

src/main/java/org/rundeck/client/api/model/ErrorResponse.java

@@ -35,7 +35,7 @@ public class ErrorResponse implements ErrorDetail {
     @Attribute
     public int apiversion;
 
-    @Attribute(name = "code")
+    @Attribute(name = "code", required = false)
     @Path("error")
     public String errorCode;
 

src/test/groovy/org/rundeck/client/api/model/ErrorResponseSpec.groovy

@@ -0,0 +1,54 @@
+package org.rundeck.client.api.model
+
+import okhttp3.MediaType
+import okhttp3.ResponseBody
+import retrofit2.Converter
+import retrofit2.Retrofit
+import retrofit2.converter.jackson.JacksonConverterFactory
+import retrofit2.converter.simplexml.SimpleXmlConverterFactory
+import spock.lang.Specification
+
+import java.lang.annotation.Annotation
+
+/**
+ * @author greg
+ * @since 12/13/17
+ */
+class ErrorResponseSpec extends Specification {
+    def "xml parse code not required"() {
+        given:
+        def retrofit = new Retrofit.Builder().baseUrl('http://test').
+                addConverterFactory(SimpleXmlConverterFactory.create()).
+                build()
+
+        when:
+        Converter<ResponseBody, ErrorResponse> converter = retrofit.responseBodyConverter(
+                ErrorResponse.class,
+                [] as Annotation[],
+                );
+        ErrorResponse result = converter.convert(ResponseBody.create(MediaType.parse('application/xml'), xmlText))
+
+        then:
+
+        result != null
+        result.errorCode == code
+        result.error == error
+        result.message == message
+        result.apiVersion == version
+
+        where:
+        xmlText                                                                                                 |
+                code  |
+                error  |
+                message | version
+        '<result error=\'true\' apiversion=\'20\'><error><message>blah</message></error></result>'              |
+                null  |
+                'true' |
+                'blah'  | 20
+        '<result error=\'true\' apiversion=\'20\'><error code=\'xyz\'><message>blah</message></error></result>' |
+                'xyz' |
+                'true' |
+                'blah'  | 20
+
+    }
+}