Move nanomesh to optional dependencies since it's not on conda-forge

pyproject.toml

@@ -38,7 +38,6 @@ dependencies = [
     "scipy",
     "tqdm",
     "pywavelets",
-    "nanomesh",
     "setuptools",
 ]
 readme = "README.md"
@@ -58,6 +57,7 @@ test = [
 ]
 extras = [
     "imageio",
+    "nanomesh",
     "numpy-stl",
     "pyevtk",
     "scikit-fmm",
@@ -137,8 +137,6 @@ python_classes = "*Test"
 python_functions = "test_*"
 testpaths = ["test", "examples"]
 norecursedirs = [".git", ".github", ".ipynb_checkpoints", "build", "dist"]
-# filterwarnings = ["error", "ignore::UserWarning", "ignore::DeprecationWarning"]
-# -p no:warnings
 
 [tool.coverage.run]
 source = ["src/porespy"]

src/porespy/generators/_micromodels.py

@@ -4,7 +4,6 @@
 import numpy as np
 import scipy.ndimage as spim
 import scipy.stats as spst
-from nanomesh import Mesher2D
 
 from porespy.generators import borders, lattice_spheres, spheres_from_coords
 from porespy.tools import _insert_disks_at_points_parallel, extend_slice
@@ -286,6 +285,12 @@ def cylindrical_pillars_mesh(
         to view online example.
 
     """
+    try:
+        from nanomesh import Mesher2D
+    except ModuleNotFoundError:
+        msg = "The nanomesh package can be installed with `pip install nanomesh`"
+        raise ModuleNotFoundError(msg)
+
     if len(shape) != 2:
         raise Exception('shape must be 2D for this function')
     if n is None: