Remove all orphans in the site, in the single user-mode.

def orphans_single(default_exec=False):
    """Remove all orphans in the site, in the single user-mode."""
    if not default_exec and executable.endswith('uwsgi'):
        # default_exec => rq => sys.executable is sane
        _executable = executable[:-5] + 'python'
    else:
        _executable = executable
    p = subprocess.Popen([_executable, '-m', 'nikola', 'orphans'],
                         stdout=subprocess.PIPE)
    p.wait()
    files = [l.strip().decode('utf-8') for l in p.stdout.readlines()]
    for f in files:
        if f:
            os.unlink(f)

    out = '\n'.join(files)
    return p.returncode, out