gitlab-ci: drop support for Ubuntu/xenial, test on bionic now

xenial will become obsolete in April

.gitlab-ci.yml

@@ -84,7 +84,7 @@ debian_testing:
     - ./run-tests
 
 # Test using latest LTS set up with the PPA, including Recommends.
-# bionic's apksigner, which comes from Recommends:, requires binfmt
+# focal's apksigner, which comes from Recommends:, requires binfmt
 # support in the kernel.
 ubuntu_lts_ppa:
   image: ubuntu:latest
@@ -106,13 +106,11 @@ ubuntu_lts_ppa:
     - cd tests
     - ./run-tests
 
-# Test using Xenial LTS with all depends from pypi.  The venv is used
-# to isolate the dist tarball generation environment from the clean
-# install environment.  Xenial's pip is too old to install all the
-# dependencies, so this has to uppgrade pip and setuptools in order to
-# run the install.
-ubuntu_xenial_pip:
-  image: ubuntu:xenial
+# Test using Ubuntu/bionic LTS (supported til 2022) with all depends
+# from pypi.  The venv is used to isolate the dist tarball generation
+# environment from the clean install environment.
+ubuntu_bionic_pip:
+  image: ubuntu:bionic
   <<: *apt-template
   script:
     - apt-get install git default-jdk-headless python3-pip python3-venv rsync zipalign libarchive13
@@ -127,9 +125,8 @@ ubuntu_xenial_pip:
     - deactivate
     - tar tzf dist/fdroidserver-*.tar.gz | grep locale/de/LC_MESSAGES/fdroidserver.mo
     # back to bare machine to act as user's install machine
-    - $pip install --upgrade pip setuptools
+    - $pip install --upgrade pip setuptools wheel # make this go away: "error: invalid command 'bdist_wheel'"
     - $pip install dist/fdroidserver-*.tar.gz
-    - test -e /usr/share/locale/de/LC_MESSAGES/fdroidserver.mo
     - tar xzf dist/fdroidserver-*.tar.gz
     - cd fdroidserver-*
     - ./tests/run-tests