Merge pull request matplotlib#29948 from dstansby/boilerplate-path-check

Author: jklymak

tools/boilerplate.py

@@ -459,5 +459,13 @@ def update_sig_from_node(node, sig):
     if len(sys.argv) > 1:
         pyplot_path = Path(sys.argv[1])
     else:
-        pyplot_path = Path(__file__).parent / "../lib/matplotlib/pyplot.py"
+        mpl_path = (Path(__file__).parent / ".." /"lib"/"matplotlib").resolve()
+        pyplot_path = mpl_path / "pyplot.py"
+        for cls in [Axes, Figure]:
+            if mpl_path not in  Path(inspect.getfile(cls)).parents:
+                raise RuntimeError(
+                    f"{cls.__name__} import path is not {mpl_path}.\n"
+                    "Please make sure your Matplotlib installation "
+                    "is from the same source checkout as boilerplate.py"
+                )
     build_pyplot(pyplot_path)