Copyright (#8970)

* Add copyright everywhere missing

* Style

utils/link_tester.py

@@ -1,4 +1,18 @@
-""" Link tester.
+# Copyright 2020 The HuggingFace Team. All rights reserved.
+#
+# 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.
+"""
+Link tester.
 
 This little utility reads all the python files in the repository,
 scans for links pointing to S3 and tests the links one by one. Raises an error