AttributeError: type object 'PrettyPrinter' has no attribute '_format_dict_items'

When running with Python 3.4

```
web_1 | Traceback (most recent call last):
web_1 | File "/code/project_name/apps/students/util.py", line 227, in EDEXML_reader
web_1 | pprint(groups_output)
web_1 | File "/usr/local/lib/python3.4/site-packages/datatyping/printer.py", line 111, in pprint
web_1 | with change_pprint_repr():
web_1 | File "/usr/local/lib/python3.4/contextlib.py", line 59, in __enter__
web_1 | return next(self.gen)
web_1 | File "/usr/local/lib/python3.4/site-packages/datatyping/printer.py", line 101, in change_pprint_repr
web_1 | old_format_dict_items = _pprint.PrettyPrinter._format_dict_items
web_1 | AttributeError: type object 'PrettyPrinter' has no attribute '_format_dict_items'
```

Looking at https://github.com/python/cpython/blob/3.4/Lib/pprint.py you can see that this was introduced in 3.5: https://github.com/python/cpython/blob/3.5/Lib/pprint.py.

Might be worth mentioning that only Python 3.5 and higher are supported!

Start by comparing the Python 3.4 and 3.5 pprint implementations referenced in the issue, then inspect the project's support documentation or metadata. Confirm the package's behavior under Python 3.4 and document that Python 3.5 and newer are supported, with the support statement easy to find.

Written by the indexing model from the issue text.