v3.1.2

Bug fixes in 3.1.2

pydot is optional again

Starting in 3.1.0, defining any StateMachine or StateChart subclass
implicitly required pydot to be installed. The metaclass invokes
_expand_docstring() for every class, and that path eagerly imported the
diagram formatter, which in turn imported pydot at module load time, so
import of a user module failed with ModuleNotFoundError: No module named 'pydot' even when no diagrams were rendered.

Two changes restore the original behavior:

• _expand_docstring now short-circuits when the class docstring contains
  no {statechart:FORMAT} placeholder, skipping the formatter import for
  the common case.
• statemachine.contrib.diagram no longer re-exports renderer classes at
  the package top level, and renderer modules are only imported when
  actually used. The dependency is only resolved when dot/svg
  rendering is requested. Mermaid and Markdown/RST formats work without
  pydot.

If your code imports DotRenderer, DotRendererConfig, MermaidRenderer
or MermaidRendererConfig directly from statemachine.contrib.diagram,
import them from the renderer submodule instead:

from statemachine.contrib.diagram.renderers.dot import DotRenderer
from statemachine.contrib.diagram.renderers.mermaid import MermaidRenderer

#622.

Other changes in 3.1.2

Security and dependency bumps

Picked up from the dependency refresh applied to main:

• ruff >=0.15.13
• pytest >=9.0.3 (CVE-2025, tmpdir handling) for py>=3.10
• django >=5.2.14 for py3.10/3.11 (multiple CVEs)
• pillow >=12.2.0 for py>=3.10 (multiple CVEs)
• transitive: urllib3 2.6.3 -> 2.7.0 (GHSA-qccp-gfcp-xxvc), requests
  2.33.1 -> 2.34.2

CI workflows: actions/checkout v4 → v5, actions/setup-python v5 → v6,
astral-sh/setup-uv v3 → v8 (pinned to v8.1.0), codecov/codecov-action
v4 → v6.