Gmsh example hardened, against calling from outside of parent folder,…

… against samples folder exists but has not needed files.

examples/show_gmsh.py

@@ -13,10 +13,9 @@
     mesh_file_tri = pathlib.Path("faces/tri/2DChannelTria.msh")
     mesh_file_quad = pathlib.Path("faces/quad/2DChannelQuad.msh")
 
-    base_samples_path = pathlib.Path("samples")
-    if not base_samples_path.exists():
-        load_sample_file.load_sample_file(str(mesh_file_tri))
-        load_sample_file.load_sample_file(str(mesh_file_quad))
+    base_samples_path = pathlib.Path(__file__).parent / "samples"
+    load_sample_file.load_sample_file(str(mesh_file_tri))
+    load_sample_file.load_sample_file(str(mesh_file_quad))
 
     # load the .msh file directly with the correct io module (meshio)
     loaded_mesh_tri = io.meshio.load(base_samples_path / mesh_file_tri)