New functionality to run test-only builds using conda packages

This MR introduces three new features:

1. A new command bdt test can run test-only conda-builds using tarballs created during a build phase
2. An equivalent new command bdt ci test can be used to run test-only builds on the CI
3. A template inside single-package.yaml can be used among packages to run specific test-only builds of themselves

bob/devtools/data/gitlab-ci/single-package.yaml

@@ -86,6 +86,42 @@ build_macosx_36:
     PYTHON_VERSION: "3.6"
 
 
+# Test targets (not normally used)
+.test_template: &test_job
+  stage: test
+  script:
+    - curl --silent "${BOOTSTRAP}" --output "bootstrap.py"
+    - python3 bootstrap.py -vv channel base
+    - source ${CONDA_ROOT}/etc/profile.d/conda.sh
+    - conda activate base
+    - bdt ci test -vv
+    - bdt ci clean -vv
+  cache: &test_caches
+    paths:
+      - miniconda.sh
+      - ${CONDA_ROOT}/pkgs/*.tar.bz2
+      - ${CONDA_ROOT}/pkgs/urls.txt
+
+
+.test_linux_template: &linux_test_job
+  <<: *test_job
+  tags:
+    - docker
+  image: continuumio/conda-concourse-ci
+  cache:
+    <<: *test_caches
+    key: "linux-cache"
+
+
+.test_macosx_template: &macosx_test_job
+  <<: *test_job
+  tags:
+    - macosx
+  cache:
+    <<: *test_caches
+    key: "macosx-cache"
+
+
 # Deploy targets
 .deploy_template: &deploy_job
   stage: deploy