Bump werkzeug from 0.14.1 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.14.1 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@0.14.1...0.15.3) Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -9,4 +9,4 @@ python-engineio==3.4.3
 python-socketio==3.1.2
 pyxtermjs==0.4.0.0
 six==1.12.0
-Werkzeug==0.14.1
+Werkzeug==0.15.3