Keyword not found recommendations

For issue #888.
I'd move the list comprehension inside `handlers.extend()` as a generator expression and would check is library excluded already earlier. Also better use kw arg style with Booleans (e.g. `code_style=True`) and dict keys can be iterated without `.keys()`. These recommendations would turn the code to something like this (untested):

    if library.name not in excluded:
        handlers.extend(library.name, utils.printable_name(name, code_style=True))
                                for name in lib.handlers)