Go back to appending sidecars with python

- Check for libraries in a pip agnostic way
- allow for adding multiple sidecars with a reusable `add_sidecars` function
- fix overwriting sidecars issue for previous python
- make it more readable

test/e2e-common.sh

@@ -42,21 +42,51 @@ function require_command() {
     fi
 }
 
-require_command ${KUBECTL_CMD}
+require_command ${KUBECTL_CMD} python3
+
+## Python Modules
+
+function require_python_module() {
+    for arg in "$@"; do
+        if ! python3 -c "import ${arg}" &> /dev/null;then
+            echo "required 'python3' module '${arg}' not be found"
+            echo "NOTE: the library name may be different but you you can try installing it via 'python3 -m pip install ${arg}'"
+            exit 1
+        fi
+    done
+}
+
+require_python_module yaml
 
 source $(dirname $0)/../vendor/github.com/tektoncd/plumbing/scripts/e2e-tests.sh
 
+# Add sidecar resources, first argument is the file
+# following arguments are string formed json/yaml processed by yaml.safe_load
+# e.g. '{"image": "registry", "name": "registry"}'
+function add_sidecars() {
+    cp ${1} ${TMPF}.read
+    SCRIPT='
+import sys, yaml
+
+f=open(0, encoding="utf-8")
+data=yaml.load(f.read(), Loader=yaml.FullLoader)
+
+sidecars = map(lambda v: yaml.safe_load(v), sys.argv[1:]) # after -c
+for sidecar in sidecars:
+  if "sidecars" in data["spec"]:
+    data["spec"]["sidecars"].append(sidecar)
+  else:
+    data["spec"]["sidecars"] = [sidecar]
+print(yaml.dump(data, default_flow_style=False))
+'
+    cat ${TMPF}.read | python3 -c "$SCRIPT" "${@:2}" > ${TMPF}
+    rm -f ${TMPF}.read
+}
+
 # Add an internal registry as sidecar to a task so we can upload it directly
 # from our tests withouth having to go to an external registry.
 function add_sidecar_registry() {
-    cp ${1} ${TMPF}.read
-
-    cat ${TMPF}.read | sed -E 's/spec:/spec:\
-  sidecars:\
-  - image: registry\
-    name: registry/' > ${TMPF}
-
-    rm -f ${TMPF}.read
+    add_sidecars ${1} '{"image":"registry", "name": "registry"}'
 }
 
 function add_task() {