Bump werkzeug from 0.15.2 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.15.2 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/0.15.2...0.15.3)

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

requirements.txt

@@ -23,4 +23,4 @@ six==1.11.0
 testresources==2.0.1
 versioneer==0.18
 wadllib==1.3.3
-Werkzeug==0.15.2
+Werkzeug==0.15.3

requirements_dev.txt

@@ -67,4 +67,4 @@ virtualenv==16.4.3
 wadllib==1.3.3
 watchdog==0.9.0
 webencodings==0.5.1
-Werkzeug==0.15.2
+Werkzeug==0.15.3