Bump werkzeug from 0.11.15 to 0.15.3

Bumps [werkzeug](https://github.com/pallets/werkzeug) from 0.11.15 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@0.11.15...0.15.3)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -39,7 +39,7 @@ requests==2.20.0
 zeep==3.1.0
 vatnumber==1.2
 vobject==0.9.3
-Werkzeug==0.14.1
+Werkzeug==0.15.3
 XlsxWriter==0.9.3
 xlwt==1.3.*
 xlrd==1.0.0