[Travis] remove bionic.pg12 and add xenial.pg10

.travis.yml

@@ -12,6 +12,7 @@ before_install:
 install:
   - pip3 install --upgrade pip
   - pip3 install -r requirements.txt
+  - pip3 freeze
 
 before_script:
   - psql -c 'create database helios;' -U postgres
@@ -26,6 +27,9 @@ jobs:
   - dist: xenial
     addons:
       postgresql: "9.6"
+  - dist: xenial
+    addons:
+      postgresql: "10"
   - dist: bionic
     addons:
       postgresql: "9.5"
@@ -38,6 +42,3 @@ jobs:
   - dist: bionic
     addons:
       postgresql: "11"
-  - dist: bionic
-    addons:
-      postgresql: "12"