[train] Ensure get_requests_for_local_unit doesn't fail on incomplete relation

This is a rebuild/make sync for charms to pickup the fix in charmhelpers to fix
any inadvertant accesses of ['ca'] in the relation data before it is available
from vault in the certificates relation.  Fix in charmhelpers is in [1].

[1] https://github.com/juju/charm-helpers/pull/832
Closes-Bug: #2028683

Change-Id: I6619dc5ca6e6a0d4123f2958560e8a3a98c89446

bindep.txt

@@ -0,0 +1 @@
+libpq-dev [platform:dpkg]

rebuild

@@ -2,4 +2,4 @@
 # when dependencies of the charm change,
 # but nothing in the charm needs to.
 # simply change the uuid to something new
-53e7e788-1178-11ec-b98d-03bb3d032abd
+6589bc12-3dbf-11ee-9037-3b2b664fa862

src/build.lock

@@ -843,6 +843,12 @@
       "type": "python_module",
       "package": "six",
       "version": "1.16.0"
+    },
+    {
+      "type": "python_module",
+      "package": "Cython",
+      "vcs": null,
+      "version": "0.29.36"
     }
   ]
 }

tox.ini

@@ -92,7 +92,8 @@ commands = stestr run --slowest {posargs}
 [testenv:pep8]
 basepython = python3
 deps = flake8==3.9.2
-       charm-tools==2.8.3
+       PyYAML==6.0.1
+       charm-tools==2.8.6
 commands = flake8 {posargs} src unit_tests
 
 [testenv:func-target]