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function update_nag() {
	global $pagenow;

	if ( is_multisite() && ! current_user_can( 'update_core' ) ) {
		return false;
	}

	if ( 'update-core.php' === $pagenow ) {
		return;
	}

	$cur = get_preferred_from_update_core();

	if ( ! isset( $cur->response ) || 'upgrade' !== $cur->response ) {
		return false;
	}

	$version_url = sprintf(
		/* translators: %s: WordPress version. */
		esc_url( __( 'https://wordpress.org/documentation/wordpress-version/version-%s/' ) ),
		sanitize_title( $cur->current )
	);

	if ( current_user_can( 'update_core' ) ) {
		$msg = sprintf(
			/* translators: 1: URL to WordPress release notes, 2: New WordPress version, 3: URL to network admin, 4: Accessibility text. */
			__( '<a href="%1$s">WordPress %2$s</a> is available! <a href="%3$s" aria-label="%4$s">Please update now</a>.' ),
			$version_url,
			$cur->current,
			network_admin_url( 'update-core.php' ),
			esc_attr__( 'Please update WordPress now' )
		);
	} else {
		$msg = sprintf(
			/* translators: 1: URL to WordPress release notes, 2: New WordPress version. */
			__( '<a href="%1$s">WordPress %2$s</a> is available! Please notify the site administrator.' ),
			$version_url,
			$cur->current
		);
	}

	wp_admin_notice(
		$msg,
		array(
			'type'               => 'warning',
			'additional_classes' => array( 'update-nag', 'inline' ),
			'paragraph_wrap'     => false,
		)
	);
}