run config tests on py3

Signed-off-by: Adrian Tschira <nota@notafile.com>

tox.ini

@@ -51,7 +51,8 @@ usedevelop=true
 commands =
     /usr/bin/find "{toxinidir}" -name '*.pyc' -delete
     coverage run {env:COVERAGE_OPTS:} --source="{toxinidir}/synapse" \
-        "{envbindir}/trial" {env:TRIAL_FLAGS:} {posargs:tests/metrics} {env:TOXSUFFIX:}
+        "{envbindir}/trial" {env:TRIAL_FLAGS:} {posargs:tests/metrics tests/config} \
+        {env:TOXSUFFIX:}
     {env:DUMP_COVERAGE_COMMAND:coverage report -m}
 
 [testenv:packaging]