Validating Natural Earth scales

lib/cartopy/feature/__init__.py

@@ -260,11 +260,20 @@ def __init__(self, category, name, scale, **kwargs):
             scale = Scaler(scale)
 
         self.scaler = scale
+        # Make sure this is a valid resolution
+        self._validate_scale()
 
     @property
     def scale(self):
         return self.scaler.scale
 
+    def _validate_scale(self):
+        if self.scale not in ('110m', '50m', '10m'):
+            raise ValueError(
+                '{} is not a valid Natural Earth scale. '.format(self.scale) +
+                'Valid scales are "110m", "50m", and "10m".'
+            )
+
     def geometries(self):
         """
         Returns an iterator of (shapely) geometries for this feature.

lib/cartopy/tests/test_features.py

@@ -1,23 +1,13 @@
-# (C) British Crown Copyright 2017 - 2018, Met Office
+# Copyright Cartopy Contributors
 #
-# This file is part of cartopy.
-#
-# cartopy is free software: you can redistribute it and/or modify it under
-# the terms of the GNU Lesser General Public License as published by the
-# Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# cartopy is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with cartopy.  If not, see <https://www.gnu.org/licenses/>.
+# This file is part of Cartopy and is released under the LGPL license.
+# See COPYING and COPYING.LESSER in the root of the repository for full
+# licensing details.
 
 from __future__ import (absolute_import, division, print_function)
 
 import cartopy.feature as cfeature
+import pytest
 
 small_extent = (-6, -8, 56, 59)
 medium_extent = (-20, 20, 20, 60)
@@ -71,3 +61,8 @@ def test_intersecting_geometries_large(self, monkeypatch):
         # '110m' when the extent is large and autoscale is True.
         auto_land.intersecting_geometries(large_extent)
         assert auto_land.scale == '110m'
+
+
+def test_bad_ne_scale():
+    with pytest.raises(ValueError, match='not a valid Natural Earth scale'):
+        cfeature.NaturalEarthFeature('physical', 'land', '30m')