Resolve "Add Ubuntu as a platform test in the CI/CD"

Closes #4 (closed)

.gitlab-ci.yml

-# SPSP Transfer Tool CI/CD
 stages:
   - test
   - deploy
@@ -25,6 +24,8 @@ centos test:
       - logs/spsp*.log
     expire_in: 1 week
     when: on_failure
+  only:
+    - merge_requests
 
 debian test:
   image: debian:10
@@ -33,7 +34,6 @@ debian test:
     - apt-get install -y netcat
     - apt-get install -y gpg
     - apt-get install -y openssh-client
-    - apt-get install -y gpg
     - mkdir -p ~/.ssh
     - echo "$SSH_PRIVATE_KEY" >> ~/.ssh/id_ed25519
     - chmod 600 ~/.ssh/id_ed25519
@@ -43,14 +43,39 @@ debian test:
   script:
     - ./spsp init --without-env
     - ./spsp test --without-env
-  inherit:
-    default: false
   artifacts:
     paths: 
       - logs/error.log
       - logs/spsp*.log
     expire_in: 1 week
     when: on_failure
+  only:
+    - merge_requests
+
+ubuntu test:
+  image: ubuntu:20.04
+  before_script:
+    - apt-get update
+    - apt-get install -y netcat
+    - apt-get install -y gnupg2
+    - apt-get install -y openssh-client
+    - mkdir -p ~/.ssh
+    - echo "$SSH_PRIVATE_KEY" >> ~/.ssh/id_ed25519
+    - chmod 600 ~/.ssh/id_ed25519
+    - echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config
+
+  stage: test
+  script:
+    - ./spsp init --without-env
+    - ./spsp test --without-env
+  artifacts:
+    paths:
+      - logs/error.log
+      - logs/spsp*.log
+    expire_in: 1 week
+    when: on_failure
+  only:
+    - merge_requests
 
 release:
   stage: deploy