GitHub actions suddenly failing to work with pipenv

Some actions I’ve had running every few hours for more than six months have started to fail this morning.

They each start with a boilerplate Python setup of pipenv like this

      - name: Checkout
        uses: actions/checkout@v2

      - name: Install Python
        uses: actions/setup-python@v2
        with:
          python-version: 3.8

      - id: install-pipenv
        name: Install pipenv
        run: |
          python -m pip install --upgrade --no-cache-dir pip
          python -m pip install --no-cache-dir pipenv
        shell: bash

      - id: cache-pipenv
        name: Cache pipenv
        uses: actions/cache@v2
        with:
          path: ~/.local/share/virtualenvs
          key: ${{ runner.os }}-pipenv-${{ hashFiles('Pipfile.lock') }}
          restore-keys: |
            ${{ runner.os }}-pipenv-

      - id: sync-pipfile
        name: Sync pipfile
        run: pipenv sync
        shell: bash

The pipenv sync step, which has worked for months, is suddenly throwing something like this:

Run pipenv sync
  pipenv sync
  shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}
  env:
    pythonLocation: /opt/hostedtoolcache/Python/3.8.11/x64
    LD_LIBRARY_PATH: /opt/hostedtoolcache/Python/3.8.11/x64/lib
Installing dependencies from Pipfile.lock (dc1cb7)...
Failed to load paths: /bin/sh: 1: /home/runner/.local/share/virtualenvs/coronavirus-tracker-Cupy5zEo/bin/python: not found

Output: 
Failed to load paths: /bin/sh: 1: /home/runner/.local/share/virtualenvs/coronavirus-tracker-Cupy5zEo/bin/python: not found

Output: 
To activate this project's virtualenv, run pipenv shell.
Alternatively, run a command inside the virtualenv with pipenv run.
All dependencies are now up-to-date!

Any ideas what’s up? Some upgrade to the containers?