Stick to jsonschema prior 2.6.0
Stick to jsonschema prior 2.6.0

Since they have broken compatibility in error messages.

Closes-Bug: #1662529

Change-Id: I8c7449297a488ea3fe90cda58e5dba0d8d4d68ff

stackforge/fuel-web,stackforge/fuel-web,stackforge/fuel-web