tests/sitecustomize.py

node: make bin() be a wrapper instead of just an alias

This includes a full backout of 59affe7e and 30d0cb27. Per the review
of the former, we'd rather adapt the API to behave like it used to (at
least for now), and take a second run at it if it shows up in our
performance numbers. I ran perfrevlogindex with and without this
change and it didn't make a measurable difference, so maybe it's fine
(despite my intuition to the contrary).

Differential Revision: https://phab.mercurial-scm.org/D2279

from __future__ import absolute_import
import os

if os.environ.get('COVERAGE_PROCESS_START'):
    try:
        import coverage
        import uuid

        covpath = os.path.join(os.environ['COVERAGE_DIR'],
                               'cov.%s' % uuid.uuid1())
        cov = coverage.coverage(data_file=covpath, auto_data=True)
        cov._warn_no_data = False
        cov._warn_unimported_source = False
        cov.start()
    except ImportError:
        pass