Bump werkzeug from 0.12.1 to 0.15.3 in /tools

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.12.1 to 0.15.3.
- [Release notes](https://github.com/pallets/werkzeug/releases)
- [Changelog](https://github.com/pallets/werkzeug/blob/master/CHANGES.rst)
- [Commits](pallets/werkzeug@0.12.1...0.15.3)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

tools/python_requirements.txt

@@ -4,7 +4,7 @@ Flask-WTF==0.14.2
 Jinja2==2.9.6
 MarkupSafe==1.0
 WTForms==2.1
-Werkzeug==0.12.1
+Werkzeug==0.15.3
 argparse==1.1
 backports-abc==0.5
 backports.ssl-match-hostname==3.5.0.1