This strikes me as a little risky -- if we want the errors to be human-readable, spewing the text of the `Exception` through the API could be problematic.  For debug purposes it would be nice (perhaps through a separate property), but I'd rather we display a generic "Sorry! An error has occurred" unless it's a custom error subclass with a "description" property, perhaps.  This could look like this:

    # We have an error object, 'exc'
    if hasattr(error, u"description"):
        error_text = error.description
    else:
        error_text = get_generic_error_description()

Alternatively, we could check the `Exception` to see if it's a languagelearning-specific subclass, then work from that.

Thoughts?