simplejson VS python json

There's currently a mix of use between the python official json module and simplejson.

One of the side effect seen is that the official json module handles less input types as simplejson until python 3.6.

This can be an issue when using the system provided Python 3 on Debian 9 which is currently 3.5

Example of such situation:

• Receiving data through the network -> bytes are returned in Python 3
• Loading data from disk using pkg_resources -> bytes are returned

From a backward compatible point of view, it would make more sense to use simplejson because of these use cases.