The method respond503() contains an exit expression.
An exit expression should only be used in rare cases. For example, if you
write a short command line script.
In most cases however, using an exit expression makes the code untestable
and often causes incompatibilities with other libraries. Thus, unless you are
absolutely sure it is required here, we recommend to refactor your code to
avoid its usage.
You can fix this by adding a namespace to your class:
When choosing a vendor namespace, try to pick something that is not too generic to avoid conflicts with other libraries.