Cap jsonschema 3.2.0 as the minimal version

Previous versions of jsonschema (<3.2.0) doesn't support python 3.8 [1].
Python 3.8 is part of the victoria supported runtimes [2] so we now force
to use jsonschema version 3.2.0 to avoid issues, remove ambiguity and ensure
that everything works with python 3 in general.

[1] https://github.com/Julian/jsonschema/pull/627
[2] https://governance.openstack.org/tc/reference/runtimes/victoria.html#python-runtimes-for-victoria

Change-Id: Id4d35c0a4bece51e4b51198123c875d302629e99

lower-constraints.txt

@@ -16,7 +16,7 @@ GitPython==1.0.1
 greenlet==0.4.10
 iso8601==0.1.11
 Jinja2==2.10
-jsonschema==2.6.0
+jsonschema==3.2.0
 keystoneauth1==3.4.0
 kombu==4.0.0
 linecache2==1.0.0

test-requirements.txt

@@ -5,7 +5,7 @@ hacking>=3.1.0,<3.2.0 # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0
 testtools>=2.2.0 # MIT
 coverage!=4.4,>=4.0 # Apache-2.0
-jsonschema>=2.6.0 # MIT
+jsonschema>=3.2.0 # MIT
 stestr>=2.0.0 # Apache-2.0
 
 fixtures>=3.0.0 # Apache-2.0/BSD