Fix get_path for 3d artists

This is a slightly adapted version of commit
1868c05

Author: tobias

lib/mpl_toolkits/mplot3d/art3d.py

@@ -448,6 +448,11 @@ def set_3d_properties(self, verts, zs=0, zdir='z'):
                            for ((x, y), z) in zip(verts, zs)]
 
     def get_path(self):
+        # docstring inherited
+        # self._path2d is not initialized until do_3d_projection
+        if not hasattr(self, '_path2d'):
+            self.axes.M = self.axes.get_proj()
+            self.do_3d_projection()
         return self._path2d
 
     def do_3d_projection(self):

lib/mpl_toolkits/mplot3d/tests/test_axes3d.py

@@ -2112,6 +2112,16 @@ def test_scatter_spiral():
     fig.canvas.draw()
 
 
+def test_Poly3DCollection_get_path():
+    # Smoke test to see that get_path does not raise
+    # See GH#27361
+    fig, ax = plt.subplots(subplot_kw={"projection": "3d"})
+    p = Circle((0, 0), 1.0)
+    ax.add_patch(p)
+    art3d.pathpatch_2d_to_3d(p)
+    p.get_path()
+
+
 def test_Poly3DCollection_get_facecolor():
     # Smoke test to see that get_facecolor does not raise
     # See GH#4067