Python 2 removal suggestions

[juliangilbey]

Hi Fabio,

I see that you've recently removed Python 2 support and done lots of cleaning up - great, thanks! It makes packaging it for Debian much more straightforward.

I have a few suggestions and questions about the current main version:

• Now that this is only Python 3, classes don't need to subclass object. There are almost 300 such occurrences in the codebase.
• Since Jython is only for Python 2.x, will the new version of pydevd support Jython any longer? If not, then the Jython-specific code could be removed.
• There is a random Python 2 file lying around: pydevd_attach_to_process/_check.py - this could be removed

Best wishes,

Julian