Bump werkzeug from 0.12.2 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.12.2 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@0.12.2...0.15.3)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.client.txt

@@ -6,7 +6,7 @@ Flask-RESTful==0.3.4
 Jinja2==2.7.2
 MarkupSafe==0.23
 SQLAlchemy==1.1.11
-Werkzeug==0.12.2
+Werkzeug==0.15.3
 itsdangerous==0.24
 python-dateutil==2.6.0
 python-gnupg==0.3.7