Update py35 jobs to py37

The upstream OpenStack default node type changed yesterday
from Ubuntu Xenial to Bionic. We have a number of jobs pegged
directly to py35 which is no longer available in Bionic.

We can either pin the py35 jobs to Xenial nodes or update them
to py36 or py37.  OpenStack is supporting both of those for the
Stein release, since StarlingX does not have any position on
Python 3 versions (yet!) I am suggesting we move straight to py37
and in the case of issues now make these jobs non-voting until
any incompatibilities are resolved.

Change-Id: I99b6fdb4fe319e51fc5bf0a2d33e67c57bfec01f
Signed-off-by: Dean Troyer <dtroyer@gmail.com>

.zuul.yaml

@@ -9,7 +9,7 @@
         - openstack-tox-linters
         - openstack-tox-pep8
         - openstack-tox-py27
-        - openstack-tox-py35
+        - openstack-tox-py37
         - stx-updates-pylint
         - stx-devstack-update
     gate:
@@ -19,7 +19,7 @@
         - openstack-tox-linters
         - openstack-tox-pep8
         - openstack-tox-py27
-        - openstack-tox-py35
+        - openstack-tox-py37
         - stx-updates-pylint
     post:
       jobs:

tox.ini

@@ -9,7 +9,7 @@
 # test suite on all supported python versions. To use it, "pip install tox"
 # and then run "tox" from this directory.
 [tox]
-envlist = linters,pep8,py27,py35,pylint
+envlist = linters,pep8,py27,py37,pylint
 minversion = 2.3
 skipsdist = True
 
@@ -103,7 +103,7 @@ recreate = True
 commands = {[testenv]commands}
            tox -c tsconfig/tsconfig  -e py27
 
-[testenv:py35]
+[testenv:py37]
 basepython = python3
 deps = {[testenv]deps}
 whitelist_externals = cp
@@ -111,7 +111,7 @@ whitelist_externals = cp
                       tox
 recreate = True
 commands = {[testenv]commands}
-           tox -c tsconfig/tsconfig  -e py35
+           tox -c tsconfig/tsconfig  -e py37
 
 [testenv:pylint]
 deps = {[testenv]deps}

tsconfig/tsconfig/tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27,py35,cover
+envlist = py27,py37,cover
 minversion = 2.3.2
 
 [testenv]