Require explicit list of publishers for each job

Publisher are required for almost every job and it's very easy to forget
to specify them and get a job that cannot be debugged. If publishers are
not required for a job, one should explicitely specify empty list of
publishers as I did here for test job and for rtfd hook.

Change-Id: I7c4923910b0e139ca3831b6450b0fbb82b618b64

jenkins/jobs/hooks.yaml

@@ -5,3 +5,4 @@
     builders:
       - revoke-sudo
       - shell: 'curl -X POST https://readthedocs.org/build/{name} >/dev/null'
+    publishers: []

jenkins/jobs/misc.yaml

@@ -9,6 +9,7 @@
 
     builders:
       - shell: 'echo ok'
+    publishers: []
 
 - job-template:
     name: 'gate-{name}-run-tests'

tools/jenkins-projects-checks.py

@@ -34,9 +34,9 @@ JOB = v.Schema({
     v.Required('builders'): v.All(list),
     v.Required('name'): v.All(str),
     v.Required('node'): v.All(str),
+    v.Required('publishers'): v.All(list),
     'description': v.All(str),
     'parameters': v.All(list),
-    'publishers': v.All(list),
     'wrappers': v.All(list)
 })
 
@@ -50,8 +50,8 @@ JOB_TEMPLATE = v.Schema({
     v.Required('builders'): v.All(list),
     v.Required('name'): v.All(str),
     v.Required('node'): v.All(str),
+    v.Required('publishers'): v.All(list),
     'description': v.All(str),
-    'publishers': v.All(list),
     'wrappers': v.All(list)
 })