Planexsc

Fix almost all pylint warnings (and a couple of errors).   Remaining warnings are about lack of documentation comments in build.py, use of some deprecated language features and some style warnings about the build_srpm function.   I will fix these shortly.

I didn't fix any errors in demjson.py.   In the next phase I'll update the code for newer Python and this file should go away.

Update (17 Jan): My original pull request failed to build xen.   I hadn't changed xen, but I've backed out everything except the first pylint warning fix-up to figure out what part of my changeset breaks the build.