tests/sitecustomize.py

ui: optimize buffered write with no label

This was spotted while making fastannotate faster again after ditching its
own formatter. Since I'm going to inline _write() into ui.write(), I decided
to include this patch in this series.

Here, the cost of '(self.label(a, label) for a in args)' was significant
in hot loops.

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