input/curl: use new class HttpStatusError

This way, IsFileNotFound() can detect status 404.

src/lib/curl/Error.hxx

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2003-2018 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef CURL_ERROR_HXX
+#define CURL_ERROR_HXX
+
+#include <stdexcept>
+
+/**
+ * Thrown when an unsuccessful status was received from the HTTP
+ * server.
+ */
+class HttpStatusError : public std::runtime_error {
+	unsigned status;
+
+public:
+	template<typename M>
+	explicit HttpStatusError(unsigned _status, M &&_msg) noexcept
+		:std::runtime_error(std::forward<M>(_msg)), status(_status) {}
+
+	unsigned GetStatus() const noexcept {
+		return status;
+	}
+};
+
+#endif