AssertionErrors are swallowed in `handle_exceptions`

[alvaro-garcia-carrasco]

Whenever an AssertionError is raised inside a method, it is handled as an InvalidParamsResponse by the exception handler and the exception does not get logged (here).

I have lots of assertion checks to verify the correct behaviour of the server and it becomes very difficult to debug errors raised by them.

[st31ny]

Catching the assertion error there is mainly a legacy thing there. Before we had InvalidParamsError, Assertions were used to signal invalid params. I guess we should get rid of that in a major release.

[bcb]

Fixed in #148