Update upstream source from tag 'upstream/3.1.1'

Update to upstream version '3.1.1'
with Debian dir abc6ff77b6e18a0ca0d156a3c926935092e08854

.travis.yml

@@ -1,37 +0,0 @@
-language: python
-dist: xenial
-
-python:
-  - "3.6"
-  - "3.7"
-  - "3.8"
-  # TODO add 3.9
-  - "3.9-dev"
-
-install: pip install tox-travis tox tox-venv
-
-# Used by the `test` stage.
-script: tox
-
-stages:
-  - test
-  - lint
-
-jobs:
-  allow_failures:
-    - python: "3.9-dev"
-
-  include:
-
-    # The `test` stage using the `python` matrix defined above
-    # is included implicitly.
-
-    - stage: lint
-      name: "Code Linting"
-      python: "3.7"
-      script: TOXENV=lint tox
-
-    - stage: check-docs
-      name: "Docs check"
-      python: "3.7"
-      script: TOXENV=check-docs tox