Add bolditalic CSS.

    :param app: Sphinx application context.
    :param env: Sphinx environment context.

def css(app, env):
    """
    Add bolditalic CSS.

    :param app: Sphinx application context.
    :param env: Sphinx environment context.
    """
    srcdir = os.path.abspath(os.path.dirname(__file__))
    cssfile = 'bolditalic.css'
    csspath = os.path.join(srcdir, cssfile)
    buildpath = os.path.join(app.outdir, '_static')
    try:
        os.makedirs(buildpath)
    except OSError:
        if not os.path.isdir(buildpath):
            raise
    copy(csspath, buildpath)
    app.add_stylesheet(cssfile)
    return