.gitlab-ci.yml: Add job to attemp to update dependencies

This will help us check if BuildStream is working with the latest
version of dependencies, as per our constraints. This job is allowed to
fail but its failure should signal that we need to add stricter
constraints in some of our `.in` requirements files.

.gitlab-ci.yml

@@ -96,7 +96,6 @@ tests-unix:
     # Since the unix platform is required to run as root, no user change required
     - ${TEST_COMMAND}
 
-
 tests-fedora-missing-deps:
   # Ensure that tests behave nicely while missing bwrap and ostree
   image: buildstream/testsuite-fedora:28-5da27168-32c47d1c
@@ -114,6 +113,22 @@ tests-fedora-missing-deps:
 
     - ${TEST_COMMAND}
 
+tests-fedora-update-deps:
+  # Check if the tests pass after updating requirements to their latest
+  # allowed version.
+  allow_failure: true
+  image: buildstream/testsuite-fedora:28-5da27168-32c47d1c
+  <<: *tests
+
+  script:
+    - useradd -Um buildstream
+    - chown -R buildstream:buildstream .
+
+    - make --always-make --directory requirements
+    - cat requirements/*.txt
+
+    - su buildstream -c "${TEST_COMMAND}"
+
 # Lint separately from testing
 lint:
   stage: test