fix: use pipx for CI actions

Pins action image to Ubuntu 24.04, to avoid future breakages.

.github/workflows/ci.yaml

@@ -9,7 +9,7 @@ on:
 jobs:
   inclusive-naming-check:
     name: Inclusive naming check
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -20,29 +20,29 @@ jobs:
 
   lint:
     name: Lint
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     steps:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Install dependencies
-        run: python3 -m pip install tox
+        run: pipx install tox
       - name: Run linters
         run: tox -e lint
 
   unit-test:
     name: Unit tests
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     steps:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Install dependencies
-        run: python3 -m pip install tox
+        run: pipx install tox
       - name: Run tests
         run: tox -e unit
 
   integration-test:
     name: Integration tests
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     needs:
       - inclusive-naming-check
       - lint
@@ -51,7 +51,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Install dependencies
-        run: python3 -m pip install tox
+        run: pipx install tox
       - name: Set up LXD
         uses: canonical/[email protected]
         with:

.github/workflows/release-libs.yaml

@@ -25,7 +25,7 @@ jobs:
 
   release-to-charmhub:
     name: Release latest version of libraries to Charmhub
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     needs:
       - ci
     steps: