tests/sitecustomize.py

subrepo: bare git repos considered dirty

Currently, if there is a bare git subrepo, but it is at the "right"
revision, calling dirty() will error because diff-index does not work
on bare repos. This patch makes it so bare subrepos are always
considered dirty.

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