Make Python shebang lines refer to python3 (cvat-ai#5739)

All scripts require Python 3; this change lets them be used in
environments where `python` is either Python 2 or missing.

`email_settings.py` is not a script, so it doesn't need a shebang line
at all.

cvat-sdk/gen/postprocess.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright (C) 2022 CVAT.ai Corporation
 #

cvat/settings/email_settings.py

@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 # Copyright (C) 2020-2022 Intel Corporation
 # Copyright (C) 2022 CVAT.ai Corporation
 #

manage.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright (C) 2018-2022 Intel Corporation
 #

site/process_sdk_docs.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright (C) 2022 CVAT.ai Corporation
 #

tests/json_to_html.py

@@ -1,10 +1,10 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright (C) 2021-2022 Intel Corporation
 #
 # SPDX-License-Identifier: MIT
 
-from json2html import *
+from json2html import json2html
 import sys
 import os
 import json