Raise exception if response from call() is CallError

[tmh-azinhal]

This PR references issue #104 .

If the response is a CallError, an exception will be raised instead of being silenced.
To maintain backwards compatibility a suppress=True keyword argument was added in Chargepoint.call.

[OrangeTux]

You can add a test? I'll come back later to

[tropxy]

A test for this is missing, then it is good to go!

[OrangeTux]

I promised some advice when it comes to writing tests for the piece of code you introduced.

In [tests/v16/test_v16_charge_point.py] you can add the tests. For the test you can reuse the base_central_system as is done in other tests in that file.

This test require a call, that is the request, and a call error. The latter is the response. Because of limitations of testing you first need prepare the response. Create an instance of ocpp.messages.CallError, turn it into json and pass it to base_central_system.route_message(). route_message() will put the response on an internal response queue.

Now you can create the request. You need to instantiate a payload from call.v16.call and 'send' that to the other end of the connection using base_central_system.call(). call() will use the response queue to look for response to its request.

Note that it's important that the request and response have the same unique id. Otherwise a response can't be matched to a request.

I hope this is enough information. If not, let me know.

[OrangeTux]

The lint job on CircleCI compains. Can you make the job happy?

[OrangeTux]

Thanks!