Fixes #734: make noise a lazy import so datasets module is usable without it (#858)

Author: brendancol

xrspatial/datasets/__init__.py

@@ -6,7 +6,6 @@
     da = None
 
 import datashader as ds
-import noise
 import numpy as np
 import pandas as pd
 import xarray as xr
@@ -81,6 +80,13 @@ def make_terrain(
         2D array of generated terrain values.
     """
 
+    try:
+        import noise
+    except ImportError:
+        raise ImportError(
+            "make_terrain requires the 'noise' package: pip install noise"
+        )
+
     if da is None:
         raise Exception("make terrain requires dask.Array (pip install dask)")