tests/sitecustomize.py

run-tests: fix hg.bat python reference

hg.bat expects to live in pythonxx/scripts and the python interpreter
to be in pythonxx. run-tests.py file layout is a little different and
python location must be fixed.

try:
    import coverage
    if hasattr(coverage, 'process_startup'):
        coverage.process_startup()
except ImportError:
    pass