Pin Pillow to 9.4.0 to work around error
Work around "'ImageDraw' object has no attribute 'textsize'" error by pinning Pillow to 9.4.0.
Example: https://gitlab.wikimedia.org/repos/releng/scap/-/jobs/119087
xrefs:
- https: //groups.google.com/g/weewx-user/c/4qz0bwgna7g
- https: //github.com/blockdiag/sphinxcontrib-blockdiag/issues/26