Bump werkzeug from 0.11.11 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.11.11 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@0.11.11...0.15.3)

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

Author: dependabot[bot]

requirements_dev.txt

@@ -11,7 +11,7 @@
 # Pin specific Flask and Werkzeug versions to make sure tests are running
 # reliably against test server code that is known to work.
 Flask==0.11.1
-Werkzeug==0.11.11
+Werkzeug==0.15.3
 
 tox