`addStep` does not catch misspelled "descriptionDone"

[tfogal]

I just got:

  exceptions.TypeError: __init__() got an unexpected keyword argument 'desciprtionDone'

after waiting a few minutes for my builder to get to that step. It would be nice if this would have been caught during `addStep', so my configuration would fail, instead of having to wait until the step ran to see my mistake.

[dustin]

You're using the old-style configuration, aren't you:

f.addStep(StepClass, decriptionDone="foo")

Don't do that :)

I *believe* the new-style catches these errors; please re-open if not.