* Enhance python_script to support "_getitem_"
In order to use dict / list structures in python scripts we need
_getitem_ allowed in the RestrictedPython environment. There is a
default_guarded_getitem included with RestrictedPython, which is a
pass through used in the Eval code paths.
* Add tests for dict/list support in python_scripts
* Lint
* Add initial version
* Fix requirements
* Prefer logging over printing
* Set executor thread name on >Py36 only
* Add tests
* Lint
* Add restrictedpython to test dependencies
* Create python_script.py
From doc:
```
However, an empty dict ({}) is treated as is. If you want to specify a list that can contain anything, specify it as dict:
>>> schema = Schema({}, extra=ALLOW_EXTRA) # don't do this
>>> try:
... schema({'extra': 1})
... raise AssertionError('MultipleInvalid not raised')
... except MultipleInvalid as e:
... exc = e
>>> str(exc) == "not a valid value"
True
>>> schema({})
{}
>>> schema = Schema(dict) # do this instead
>>> schema({})
{}
>>> schema({'extra': 1})
{'extra': 1}
```
