Fix issue with new files

src/rapids_pre_commit_hooks/copyright.py

@@ -210,7 +210,11 @@ def the_check(linter, args):
         except KeyError:
             return
 
-        old_content = changed_file.data_stream.read().decode("utf-8")
+        old_content = (
+            changed_file.data_stream.read().decode("utf-8")
+            if changed_file is not None
+            else None
+        )
         apply_copyright_check(linter, old_content)
 
     return the_check

test/rapids_pre_commit_hooks/test_copyright.py

@@ -683,6 +683,8 @@ def file_contents_modified(num):
     git_repo.index.move(["file2.txt", "file5.txt"])
     git_repo.index.commit("Rename file2.txt to file5.txt")
 
+    write_file("file6.txt", file_contents(6))
+
     def mock_repo_cwd():
         return patch("os.getcwd", Mock(return_value=git_repo.working_tree_dir))
 
@@ -724,6 +726,11 @@ def mock_apply_copyright_check():
         copyright_checker(linter, None)
         apply_copyright_check.assert_called_once_with(linter, file_contents(4))
 
+    linter = Linter("file6.txt", file_contents(6))
+    with mock_apply_copyright_check() as apply_copyright_check:
+        copyright_checker(linter, None)
+        apply_copyright_check.assert_called_once_with(linter, None)
+
     #############################
     # branch-2 is target branch
     #############################
@@ -750,3 +757,8 @@ def mock_apply_copyright_check():
     with mock_apply_copyright_check() as apply_copyright_check:
         copyright_checker(linter, None)
         apply_copyright_check.assert_called_once_with(linter, file_contents(4))
+
+    linter = Linter("file6.txt", file_contents(6))
+    with mock_apply_copyright_check() as apply_copyright_check:
+        copyright_checker(linter, None)
+        apply_copyright_check.assert_called_once_with(linter, None)