tests/sitecustomize.py

osx: override default exclude filter for pkgbuild

To quote `man 1 pkgbuild`:

     --filter filter-expression
                 By default, --root will include the entire contents of the
                 given root-path in the package payload, except for any .svn
                 or CVS directories, and any .DS_Store files. You can override
                 these default filters by specifying one or more --filter
                 options. Each filter-expression is an re_format(7)
                 ``extended'' expression: any path in the root which matches
                 any of the given expressions will be excluded from the pack-
                 age payload. (Note that specifying even one --filter inhibits
                 the default filters, so you must respecify the default fil-
                 ters if you still want them to be used.)

It turns out the default filter these days *also* includes .git and
.hg. Notice how that filter expression is a regular expression?  That
(presumably unintentionally) prevents a file named "chg" or "_hg" from
getting included in the distribution. Many many thanks to spectral@
for trying to include a _hg file which led us to figure this bug out.

Bug filed with Apple for this as rdar://problem/32437369, mentioning
both the gap in documentation and the wrong defaults.

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