[Travis] try to update travis tests matrix

.travis.yml

@@ -2,6 +2,7 @@ sudo: false
 language: python
 python:
   - "3.7"
+  - "3.8"
 
 os: linux
 
@@ -19,24 +20,24 @@ script: "python3 -Wall manage.py test"
 
 jobs:
   include:
-  - dist: trusty
+  - dist: xenial
     addons:
-      postgresql: "9.3"
-  - dist: trusty
+      postgresql: "9.5"
+  - dist: xenial
     addons:
-      postgresql: "9.4"
-  - dist: trusty
+      postgresql: "9.6"
+  - dist: bionic
     addons:
       postgresql: "9.5"
-  - dist: trusty
+  - dist: bionic
     addons:
       postgresql: "9.6"
-  - dist: xenial
+  - dist: bionic
     addons:
-      postgresql: "9.4"
-  - dist: xenial
+      postgresql: "10"
+  - dist: bionic
     addons:
-      postgresql: "9.5"
-  - dist: xenial
+      postgresql: "11"
+  - dist: bionic
     addons:
-      postgresql: "9.6"
+      postgresql: "12"