Move requirements job failure msg into log

A failure on the requirements job currently uses a custom
failure-message.  The problem is that this custom message doesn't
match the gerrit magic for extracting failures and showing them in the
"Jenkins check" box.

This means that jenkins votes -1, but you don't see any failures
unless you go and click the "toggle ci" button.  This leads to
confusion and people rechecking unnecessarily.

The message doesn't seem particlarly important; the linked page is
just the regular documentation and isn't exactly a trouble-shooting
guide.  Thus move the message and link into the job output so this job
remains consistent.  The message stays similar but without the link so
it matches.

Change-Id: I2af14c7993e097178c4cc7ee894804c005148523

jenkins/scripts/project-requirements-change.py

@@ -253,6 +253,8 @@ def main():
 
     # report the results
     if failed or head_reqs.failed or branch_reqs.failed:
+        print("*** Incompatible requirement found!")
+        print("*** See http://docs.openstack.org/developer/requirements")
         sys.exit(1)
     print("Updated requirements match openstack/requirements.")
 

zuul/layout.yaml

@@ -2591,7 +2591,7 @@ jobs:
     branch: ^(?!master).*$
 
   - name: ^gate-.*-requirements$
-    failure-message: FAILURE Incompatible requirement found; see http://docs.openstack.org/developer/requirements/
+    failure-message: FAILURE Incompatible requirement found
     files:
       - '^tools/.*-requires$'
       - '^.*requirements.txt$'