CI: Manually download Cartopy maps

This works around Cartopy <=0.19 on PyPI using an outdate URL for the
Natural Earth data. Instead of worrying about caching, just download
directly from S3 using Cartopy's own download code.

.github/workflows/docs.yml

@@ -79,6 +79,9 @@ jobs:
         python -m pip install -c ci/${{ matrix.dep-versions }} numpy
         python -m pip install -r ci/doc_requirements.txt -r ci/extra_requirements.txt -c ci/${{ matrix.dep-versions }}
 
+    - name: Download Cartopy Maps
+      run: ci/download_cartopy_maps.py
+
     - name: Install self
       run: python -m pip install -c ci/${{ matrix.dep-versions }} .
 

.github/workflows/tests-pypi.yml

@@ -94,6 +94,10 @@ jobs:
     - name: Install test dependencies
       run: python -m pip install -r ci/test_requirements.txt -c ci/${{ matrix.dep-versions }}
 
+    - name: Download Cartopy Maps
+      if: ${{ matrix.no-extras != 'No Extras' }}
+      run: ci/download_cartopy_maps.py
+
     - name: Install
       run: python -m pip install -c ci/${{ matrix.dep-versions }} .
 

ci/download_cartopy_maps.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python
+# Copyright (c) 2021 MetPy Developers.
+"""Explicitly download needed Cartopy maps."""
+from cartopy.io import config, Downloader
+
+AWS_TEMPLATE = ('https://naturalearth.s3.amazonaws.com/{resolution}_'
+                '{category}/ne_{resolution}_{name}.zip')
+
+
+def grab_ne(category, feature, res):
+    """Download the correct Natural Earth feature using Cartopy."""
+    download = Downloader.from_config(('shapefiles', 'natural_earth'))
+    download.path({'category': category, 'name': feature, 'resolution': res, 'config': config})
+
+
+if __name__ == '__main__':
+    # Need to override the pre-Cartopy 0.20 URL to use S3
+    config['downloaders'][('shapefiles', 'natural_earth')].url_template = AWS_TEMPLATE
+
+    for feat in ['admin_0_boundary_lines_land', 'admin_1_states_provinces_lakes']:
+        for r in ['110m', '50m', '10m']:
+            grab_ne('cultural', feat, r)
+
+    for feat, r in [('coastline', '10m'), ('coastline', '50m'), ('coastline', '110m'),
+                    ('lakes', '10m'), ('lakes', '50m'),
+                    ('land', '10m'), ('land', '50m'), ('land', '110m'),
+                    ('ocean', '110m'), ('ocean', '50m'),
+                    ('rivers_lake_centerlines', '10m'), ('rivers_lake_centerlines', '110m')]:
+        grab_ne('physical', feat, r)