Handle non-subscriptable path in humanize_error

[kellerza]

Description

_nested_getitem currently raises an exception when the error path contains a non-subscriptable entity (e.g. None, int)

data = None, path = ['input_select', 'hello', 'options', 0]

    def _nested_getitem(data, path):
        for item_index in path:
            try:
>               data = data[item_index]
E               TypeError: 'NoneType' object is not subscriptable

../hv/lib64/python3.4/site-packages/voluptuous/humanize.py:11: TypeError

This happens in the following situations:
Data to be validated: {'key1': None} or {'key1': 1}
Schema: vol.Schema('key1': vol.All(ensure_list, [str]))

ensure_list mutates the data into an array, if [str] fails the exception contains [0] as an index in the mutated data, but the exception can only be logged using the original (non-list) data, in which case [0] cannot be applied to a non-subscriptable path like int[0] or None[0].

[tusharmakkar08]

@kellerza Shouldn't it return None instead?

[kellerza]

The advantage of resolving until you hit a failure (by breaking out) is that it helps you in the correct direction.

Happy to comply either way, your call

[tusharmakkar08]

Let's keep it consistent with KeyError and IndexError. You can add it in Line 12 and update the comment correspondingly.

[tusharmakkar08]

@kellerza : Merged 🍰