* same behaviour for shellRunner and execRunner wrt errors and stdout
* replace shouldFail with shouldFailOnCommand
* [formatting only] format struct
* Move to regex for execptions and stdout
* shrink code
There was some command parsing with failure in case it started with fail. That is
IMO less transparent. Now we prepare more explicit with a failure from outside. This
enables us to prepare an error like we expect it in the free wild.
