Merge branch 'feature/sles151' into 'master'

Drop SLES v15.1

See merge request !17

.gitlab-ci.yml

@@ -143,23 +143,6 @@ upload/SUSE/15.2:
   dependencies:
     - build/sles/15.2
 
-build/sles/15.1:
-  <<: *build
-  variables:
-    DOCKER_IMAGE: sles/15.1
-
-test/sles/15.1:
-  <<: *test
-  variables:
-    DOCKER_IMAGE: sles/15.1
-  dependencies:
-    - build/sles/15.1
-
-upload/SUSE/15.1:
-  <<: *upload
-  dependencies:
-    - build/sles/15.1
-
 build/sles/12.5:
   <<: *build
   variables: