Bugfix: do not display a enum raw value but a human explanation

src/com/sheepit/client/Error.java

@@ -124,6 +124,8 @@ public class Error {
 				return "This client is too old, you need to update it";
 			case AUTHENTICATION_FAILED:
 				return "Failed to authenticate, please check your login and password";
+			case DOWNLOAD_FILE:
+				return "Error will downloading project's needed files. Will try another project in a few minutes.";
 			case NOOUTPUTFILE:
 				return "Renderer has generated no output file, possibly a wrong project configuration or you are missing required libraries. Will try another project in a few minutes.";
 			case RENDERER_CRASHED: