Bump werkzeug from 0.11.10 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.11.10 to 0.15.3.
- [Release notes](https://github.com/pallets/werkzeug/releases)
- [Changelog](https://github.com/pallets/werkzeug/blob/master/CHANGES.rst)
- [Commits](https://github.com/pallets/werkzeug/compare/0.11.10...0.15.3)

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

requirements.txt

@@ -8,7 +8,7 @@ python-mimeparse==1.5.2
 python-socketio==1.4.4
 PyYAML==4.2b1
 requests==2.20.0
-Werkzeug==0.11.10
+Werkzeug==0.15.3
 httplib2==0.18.0
 flask-classy==0.6.10
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