diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-admin/includes/class-automatic-upgrader-skin.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-admin/includes/class-automatic-upgrader-skin.php	Mon Oct 14 17:39:30 2019 +0200
@@ -0,0 +1,113 @@
+<?php
+/**
+ * Upgrader API: Automatic_Upgrader_Skin class
+ *
+ * @package WordPress
+ * @subpackage Upgrader
+ * @since 4.6.0
+ */
+
+/**
+ * Upgrader Skin for Automatic WordPress Upgrades
+ *
+ * This skin is designed to be used when no output is intended, all output
+ * is captured and stored for the caller to process and log/email/discard.
+ *
+ * @since 3.7.0
+ * @since 4.6.0 Moved to its own file from wp-admin/includes/class-wp-upgrader-skins.php.
+ *
+ * @see Bulk_Upgrader_Skin
+ */
+class Automatic_Upgrader_Skin extends WP_Upgrader_Skin {
+	protected $messages = array();
+
+	/**
+	 * Determines whether the upgrader needs FTP/SSH details in order to connect
+	 * to the filesystem.
+	 *
+	 * @since 3.7.0
+	 * @since 4.6.0 The `$context` parameter default changed from `false` to an empty string.
+	 *
+	 * @see request_filesystem_credentials()
+	 *
+	 * @param bool   $error                        Optional. Whether the current request has failed to connect.
+	 *                                             Default false.
+	 * @param string $context                      Optional. Full path to the directory that is tested
+	 *                                             for being writable. Default empty.
+	 * @param bool   $allow_relaxed_file_ownership Optional. Whether to allow Group/World writable. Default false.
+	 * @return bool True on success, false on failure.
+	 */
+	public function request_filesystem_credentials( $error = false, $context = '', $allow_relaxed_file_ownership = false ) {
+		if ( $context ) {
+			$this->options['context'] = $context;
+		}
+		// TODO: fix up request_filesystem_credentials(), or split it, to allow us to request a no-output version
+		// This will output a credentials form in event of failure, We don't want that, so just hide with a buffer
+		ob_start();
+		$result = parent::request_filesystem_credentials( $error, $context, $allow_relaxed_file_ownership );
+		ob_end_clean();
+		return $result;
+	}
+
+	/**
+	 *
+	 * @return array
+	 */
+	public function get_upgrade_messages() {
+		return $this->messages;
+	}
+
+	/**
+	 *
+	 * @param string|array|WP_Error $data
+	 */
+	public function feedback( $data ) {
+		if ( is_wp_error( $data ) ) {
+			$string = $data->get_error_message();
+		} elseif ( is_array( $data ) ) {
+			return;
+		} else {
+			$string = $data;
+		}
+		if ( ! empty( $this->upgrader->strings[ $string ] ) )
+			$string = $this->upgrader->strings[ $string ];
+
+		if ( strpos( $string, '%' ) !== false ) {
+			$args = func_get_args();
+			$args = array_splice( $args, 1 );
+			if ( ! empty( $args ) )
+				$string = vsprintf( $string, $args );
+		}
+
+		$string = trim( $string );
+
+		// Only allow basic HTML in the messages, as it'll be used in emails/logs rather than direct browser output.
+		$string = wp_kses( $string, array(
+			'a' => array(
+				'href' => true
+			),
+			'br' => true,
+			'em' => true,
+			'strong' => true,
+		) );
+
+		if ( empty( $string ) )
+			return;
+
+		$this->messages[] = $string;
+	}
+
+	/**
+	 */
+	public function header() {
+		ob_start();
+	}
+
+	/**
+	 */
+	public function footer() {
+		$output = ob_get_clean();
+		if ( ! empty( $output ) )
+			$this->feedback( $output );
+	}
+}