Uncap jsonschema

We have jsonschema capped at a fairly old version. Other than some
specific releases, it looks like keeping it below 3.0 was added in
I943fd68b9fab3bce1764305a5058df5339470757 without really any explanation
why.

In order to update to a 3.x release we need to:
1. Remove the cap from global-requirements.txt (see Depends-On), leaving
   upper-constraints.txt at a 2.x release
2. Remove the cap from all consumers (this change)
3. Release a new version of consumers that are published to pypi
4. Update upper-constraints.txt with those new releases
5. Update jsonschema in upper-constraints.txt to a 3.X release
   (See: https://review.openstack.org/649789)
6. Test consumers with the change from 5.
7. [Optional] fix issues in consumers that arise from 6.
8. Merge the change from 5.

Change-Id: I193b71b0ee6fe1abffa0d6aa30ddb1412daf6da0
Co-Authored-by: Sean McGinnis <sean.mcginnis@gmail.com>
Depends-On: https://review.openstack.org/649669

doc/requirements.txt

@@ -1,7 +1,8 @@
 # The order of packages is significant, because pip processes them in the order
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
-sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.4'  # BSD
 os-client-config>=1.28.0 # Apache-2.0
 openstackdocstheme>=1.18.1 # Apache-2.0
 reno>=2.5.0 # Apache-2.0

requirements.txt

@@ -5,7 +5,7 @@ pbr!=2.1.0,>=2.0.0 # Apache-2.0
 requests>=2.14.2 # Apache-2.0
 six>=1.10.0 # MIT
 stevedore>=1.20.0 # Apache-2.0
-jsonschema<3.0.0,>=2.6.0 # MIT
+jsonschema>=2.6.0 # MIT
 
 # Oslo Packages
 oslo.i18n>=3.15.3 # Apache-2.0