change pep440 call from python to regex

.github/workflows/_container.yml

@@ -5,6 +5,8 @@ on:
 env:
   GCR_IMAGE: ghcr.io/diamondlightsource/blueapi
   HELM_VERSION: 3.10.3
+  PEP_440_REGEX: v?(?:(?:(?<epoch>[0-9]+)!)?(?<release>[0-9]+(?:\.[0-9]+)*)(?<pre>[-_\.]?(?<preLabel>(a|b|c|rc|alpha|beta|pre|preview))[-_\.]?(?<preNumber>[0-9]+)?)?(?<post>(?:-(?<postNumber0>[0-9]+))|(?:[-_\.]?(?<postLabel>post|rev|r)[-_\.]?(?<postNumber1>[0-9]+)?))?(?<dev>[-_\.]?(?<devLabel>dev)[-_\.]?(?<devNumber>[0-9]+)?)?)(?:\+(?<local>[a-z0-9]+(?:[-_\.][a-z0-9]+)*))?
+  # https://regex101.com/library/M7QMAp
 
 jobs:
   build_container:
@@ -18,21 +20,14 @@ jobs:
           fetch-depth: 0
       - name: Validate PEP 440 version compliance
         run: |
-          python -m pip install packaging
-          python -c "
-      import re
-      from packaging.version import Version, InvalidVersion
-
-      ref = '${GITHUB_REF##*/}'
-      try:
-          version = Version(ref)
-          print(f'PEP 440 compliant version: {version}')
-      except InvalidVersion:
-          print(f'Invalid PEP 440 version: {ref}')
-          exit(1)
-        "
-
-
+          ref="${{ github.ref_name }}"
+          my_regex=${{env.PEP_440_REGEX}}
+          if [[ "$ref" =~ $my_regex ]]; then
+            echo "PEP 440 compliant version: $ref"
+          else
+            echo "Invalid PEP 440 version: $ref"
+            exit 1
+          fi
       - name: Set up Docker Buildx
         id: buildx
         uses: docker/setup-buildx-action@v3