Move safety checks to new Zuul job

Moves safety checks from pep8 linting to a new Zuul job. This allows
voting to be disabled on the job when the safety check database is down.

Changes basepython to python3 for safety job.

Change-Id: I29af8af244d45fbbe008c5efc341c1407c809539

.zuul.yaml

@@ -23,12 +23,14 @@
     check:
       jobs:
         - openstack-tox-pep8
+        - dependency-vulnerability-check
         - airship-pegleg-docker-build-gate-ubuntu_xenial
         - airship-pegleg-docker-build-gate-ubuntu_bionic
         - airship-pegleg-docker-build-gate-opensuse
     gate:
       jobs:
         - openstack-tox-pep8
+        - dependency-vulnerability-check
         - airship-pegleg-docker-build-gate-ubuntu_xenial
         - airship-pegleg-docker-build-gate-ubuntu_bionic
         - airship-pegleg-docker-build-gate-opensuse
@@ -45,6 +47,15 @@
       - name: primary
         label: ubuntu-xenial
 
+- job:
+    name: dependency-vulnerability-check
+    parent: openstack-tox
+    voting: false
+    timeout: 600
+    nodeset: spyglass-single-node
+    vars:
+      tox_envlist: safety
+
 - job:
     name: airship-pegleg-docker-build-gate-ubuntu_xenial
     timeout: 1800

tox.ini

@@ -35,9 +35,6 @@ deps =
 commands =
   bash -c "{toxinidir}/tools/gate/whitespace-linter.sh"
   bandit -r pegleg -n 5
-  safety check -r {toxinidir}/requirements.txt \
-               -r {toxinidir}/test-requirements.txt \
-               -r {toxinidir}/doc/requirements.txt --bare
   flake8 {toxinidir}/pegleg
 whitelist_externals =
   bash
@@ -57,6 +54,7 @@ basepython = python3
 commands = bandit -r pegleg -n 5
 
 [testenv:safety]
+basepython = python3
 deps =
     safety
 commands =