[CI-4521] Add exception message (#165)

Author: stanlp1

constructorio-client/src/main/java/io/constructor/client/ConstructorIO.java

@@ -2024,7 +2024,7 @@ protected static String getResponseBody(Response response) throws ConstructorExc
                 errorCode = response.code();
             }
         } catch (Exception e) {
-            errorMessage = "[HTTP " + response.code() + "]";
+            errorMessage = "[HTTP " + response.code() + "] Exception: " + e.getMessage();
         } finally {
             response.close();
         }