Bump flask from 0.12.2 to 1.0

Bumps [flask](https://github.com/pallets/flask) from 0.12.2 to 1.0.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/master/CHANGES.rst)
- [Commits](pallets/flask@0.12.2...1.0)

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

Author: dependabot[bot]

requirements.client.txt

@@ -1,7 +1,7 @@
 # Flask 0.11 does not work yet.
 six
 aniso8601==1.2.0
-Flask==0.12.2
+Flask==1.0
 Flask-RESTful==0.3.4
 Jinja2==2.7.2
 MarkupSafe==0.23