Support running on Python 3

[ncoghlan]

This patch series covers:

• initial single-source 2/3 support via python-modernize
• subsequent updates to get tests to same state on both 2 & 3

[bkabrda]

Note: when running redhawk with this patch series on Python 3, it will only work on common subset of Python 2 and Python 3. IOW, it won't work on e.g.

try:
    pass
except Exception, e: # py2 only syntax
    pass

or

async def foo(): # py3 only syntax
    pass

If run on Python 2, it will still analyze Python 2 code correctly. Analyzing Python 3 constructs when running on Python 3 will require some additional work (adding Converters and Nodes for these constructs).

[spranesh]

This is the only file that the six module is now being imported for. In this file, filter is used only at Line 226. Replacing it with list(filter(..)) will enable us to remove this import, thereby removing six as a dependency altogether.

[bkabrda]

Good point, will do.

[spranesh]

I have three comments:

• Adding a ConvertList method will clean up lots of code in the converters due to the list(map(..)) pattern
• Dependency on six module can be removed by changing filter in one place
• The Try node was added for Issue Support analysing new Python 3 syntactic constructs #2. All the other changes here are for Issue Python 3 #1. If you are planning on working that in the near future, it would be good to separate that out into another PR?

We will also need a way to separate out if-else pattern when Python 3 support starts. I will think about a way of doing so in the near future.

Change is looking good. Please address the above and I'll accept the Pull request. Thanks for doing this!

[bkabrda]

So I think I addressed all of your points, but I started testing on Python 3.5 and there seem to be some new test failures, so I'm going to investigate them. Please don't merge yet.

[bkabrda]

Ok, fixed Python 3.5 compatibility and pushed. Ready to be re-reviewed and merged.

[spranesh]

Changes look good - I've merged this to master. Thanks everybody for pitching in and helping fix this issue. Appreciate this! :-)

@bkabrda: Good spot with ConverListOfStatements!

[bkabrda]

Thanks a lot for the review and for accepting, @spranesh!

[jpopelka]

Thanks @bkabrda @spranesh @ncoghlan !

[spranesh]

Thanks @bkabrda @ncoghlan @jpopelka for your contributions! I've just released a version containing these changes (and some bug fixes). This version will enable redhawk to run via Python3.

However, it may still barf when analyzing some Python3 codebases. This is important, but will take significant development time to fix (Issue #2 and Issue #3).