Use date for age based cache invalidation (techservicesillinois#77)

The script weekold.py was used to invalidate a cache after a week.
The script worked but the cache contents were not updated since
cache contents are saved only on a cache miss. The only way to
update a Github Actions cache is to change the key.

This commit removes the weekold.py script, and inserts the week
number in the cache key name. This ensures that the cache can never
be more than a week old.

.github/workflows/cicd.yml

@@ -84,37 +84,32 @@ jobs:
         path: ${{ steps.pip-cache.outputs.dir }}
         key: ${{ runner.os }}-pip-${{ secrets.CACHE_VERSION }}
 
+    - name: Get date
+      id: date
+      run: echo "::set-output name=week::$(date '+%U')"
+
     - name: Cache tox virtualenv
       id: tox
       uses: actions/cache@v2
       with:
         path: |
             **/.tox
             **/cache
-        key: ${{ runner.os }}-${{ matrix.python-version }}-tox-${{ hashFiles('**/setup.py', '**/tox.ini') }}-${{ secrets.CACHE_VERSION }}
+        key: ${{ runner.os }}-${{ matrix.python-version }}-tox-${{ hashFiles('**/setup.py', '**/tox.ini') }}-${{ steps.date.outputs.week }}-${{ secrets.CACHE_VERSION }}
 
-    - name: Is cache old?
+    # touch cache and tox env so make will not rebuild them
+    - name: Update timestamps
       if: steps.tox.outputs.cache-hit == 'true'
-      id: age
-      run: |
-        set -x
-        if python scripts/weekold.py cache/*
-        then
-            # touch cache and tox env so make will not rebuild them
-            touch -c cache .tox/wheel/pyvenv.cfg
-        else
-            # If cache is old force rebuild of tox virtualenv(s)
-            rm -rf .tox cache
-        fi
+      run: touch -c cache .tox/wheel/pyvenv.cfg
       shell: bash
 
     - name: Install system dependencies
-      if: matrix.os == 'ubuntu-latest' && (steps.tox.outputs.cache-hit != 'true' || steps.age.outputs.weekold == 'True')
+      if: matrix.os == 'ubuntu-latest' && steps.tox.outputs.cache-hit != 'true'
       run: |
         sudo apt-get install -y libxml2-dev libxslt-dev
 
     - name: Upgrade pip
-      if: steps.tox.outputs.cache-hit != 'true' || steps.age.outputs.weekold == 'True'
+      if: steps.tox.outputs.cache-hit != 'true'
       run: |
         python -m pip install --upgrade --upgrade-strategy eager pip
 
@@ -123,11 +118,11 @@ jobs:
         python -m pip install --upgrade --upgrade-strategy eager tox wheel
 
     - name: Update Python wheel cache
-      if: steps.tox.outputs.cache-hit != 'true' || steps.age.outputs.weekold == 'True'
+      if: steps.tox.outputs.cache-hit != 'true'
       run: make cache
 
     - name: Install
-      if: steps.tox.outputs.cache-hit != 'true' || steps.age.outputs.weekold == 'True'
+      if: steps.tox.outputs.cache-hit != 'true'
       run: make install
 
     - name: Installed dependencies