fixup! test_json_schema: resolve `request` and `response` schemas

use six for python3 compatibility
2 jobs for fix/caucase-pem-slapos-testing
Status Job ID Name Coverage
  External
failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

09:40:33

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3