Add make clean

[sirex]

Some times environment has to be cleaned and rebuild from scratch.

See: https://groups.google.com/d/topic/python-dirbtuves/a5nMBPJXYM4/discussion

[iakovleva]

Should I merge this branch into remote master at first and then merge remote and my local branches?

[sirex]

I think you can merge this to master, then checkout master, pull changes, run make clean (if you still need this) and then switch back to you branch.

make clean would do the same thing on any branch, because it works on files excluded from version control, so if you still have issue after python upgrade, then it is enough to run make clean while your active branch is master, then switch back to you branch and run make to rebuild you environment to make it use upgraded python.

[iakovleva]

Thank you, this worked for me.