format multiline errors properly in acquire progress

format multiline errors properly in acquire progress

Together with the GlobalError change this allows us to add errors
spanning multiple lines, just that we control GlobalError while the
acquire progress is dealt with potentially by individual clients which
might or might not need to be adapted.

This isn't critical through as it either just works as expected anyhow
or is a minor styling thing (after all, all this commit does it add two
spaces to indent the lines a bit…).