fix: Check project id before starting gateway (#4412)

cmd/gateway-gcs-errors.go

@@ -0,0 +1,27 @@
+/*
+ * Minio Cloud Storage, (C) 2017 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import "errors"
+
+var (
+	// Project is format is not valid
+	errGCSInvalidProjectID = errors.New("invalid project id")
+
+	// Multipart identifier is not in the correct form
+	errGCSNotValidMultipartIdentifier = errors.New("Not a valid multipart identifier")
+)