run-tests: avoid os.getcwdb() on Windows Any call to this issues a DeprecationWarning about the Windows bytes API being deprecated. There are a handful of these calls in core, but test-run-tests.t was littered with these, as it's printed everytime run-tests.py is launched. I'm not sure what the long term strategy for Unicode on Windows in the test runner is, but this seems no worse than the current conversion strategy.

run-tests: quote PYTHON when spawning a subprocess Same reason as 5abc47d4ca6b. This covers running *.py tests, as well as inline python blocks. I didn't hit the path around line 3079, but it seems correct to quote.