def newer_group(sources, target, missing='error'):
    """Return true if 'target' is out-of-date with respect to any file
    listed in 'sources'.  In other words, if 'target' exists and is newer
    than every file in 'sources', return false; otherwise return true.
    'missing' controls what we do when a source file is missing; the
    default ("error") is to blow up with an OSError from inside 'stat()';
    if it is "ignore", we silently drop any missing source files; if it is
    "newer", any missing source files make us assume that 'target' is
    out-of-date (this is handy in "dry-run" mode: it'll make you pretend to
    carry out commands that wouldn't work because inputs are missing, but
    that doesn't matter because you're not actually going to run the
    commands).
    """
    # If the target doesn't even exist, then it's definitely out-of-date.
    if not os.path.exists(target):
        return 1

    # Otherwise we have to find out the hard way: if *any* source file
    # is more recent than 'target', then 'target' is out-of-date and
    # we can immediately return true.  If we fall through to the end
    # of the loop, then 'target' is up-to-date and we return false.
    from stat import ST_MTIME

    target_mtime = os.stat(target)[ST_MTIME]
    for source in sources:
        if not os.path.exists(source):
            if missing == 'error':  # blow up when we stat() the file
                pass
            elif missing == 'ignore':  # missing source dropped from
                continue  # target's dependency list
            elif missing == 'newer':  # missing source means target is
                return 1  # out-of-date

        source_mtime = os.stat(source)[ST_MTIME]
        if source_mtime > target_mtime:
            return 1
    else:
        return 0
Return true if 'target' is out-of-date with respect to any file
    listed in 'sources'.  In other words, if 'target' exists and is newer
    than every file in 'sources', return false; otherwise return true.
    'missing' controls what we do when a source file is missing; the
    default ("error") is to blow up with an OSError from inside 'stat()';
    if it is "ignore", we silently drop any missing source files; if it is
    "newer", any missing source files make us assume that 'target' is
    out-of-date (this is handy in "dry-run" mode: it'll make you pretend to
    carry out commands that wouldn't work because inputs are missing, but
    that doesn't matter because you're not actually going to run the
    commands).
    
product/gradle-plugin/src/main/python/setuptools/_distutils/dep_util.py