MNT: Updating to MPL 3.2 minimum

Pin minimum CI to 3.2.1 because that has the test label
at conda-forge which we need for the image tests. Remove other
image comparison checks for less than 3.2.

.github/workflows/ci-testing.yml

@@ -30,7 +30,7 @@ jobs:
         if: matrix.python-version == '3.8' && matrix.os == 'ubuntu-latest'
         id: minimum-packages
         run: |
-          echo "PACKAGES=cython=0.29.15 matplotlib=3.1 numpy=1.19 owslib=0.19.1 pyproj=3.0 proj=8.0 scipy=1.4.0 shapely=1.6.4" >> $GITHUB_ENV
+          echo "PACKAGES=cython=0.29.15 matplotlib-base=3.2.1 numpy=1.19 owslib=0.19.1 pyproj=3.0 proj=8.0 scipy=1.4.0 shapely=1.6.4" >> $GITHUB_ENV
 
       - name: Latest packages
         if: steps.minimum-packages.conclusion == 'skipped'

INSTALL

@@ -109,7 +109,7 @@ Further information about the required dependencies can be found here:
 **Python** 3.8 or later (https://www.python.org/)
     Python 2 support was removed in v0.19.
 
-**Matplotlib** 3.1 or later (https://matplotlib.org/)
+**Matplotlib** 3.2 or later (https://matplotlib.org/)
     Python package for 2D plotting. Python package required for any
     graphical capabilities.
 

lib/cartopy/tests/mpl/test_examples.py

@@ -5,7 +5,6 @@
 # licensing details.
 
 import matplotlib.pyplot as plt
-from packaging.version import parse as parse_version
 import pytest
 
 import cartopy.crs as ccrs
@@ -35,7 +34,7 @@ def test_global_map():
 @pytest.mark.natural_earth
 @pytest.mark.mpl_image_compare(filename='contour_label.png',
                                tolerance=(9.9
-                                          if MPL_VERSION < parse_version('3.2')
+                                          if MPL_VERSION.release[:2] < (3, 3)
                                           else 0.5))
 def test_contour_label():
     from cartopy.tests.mpl.test_caching import sample_data

lib/cartopy/tests/mpl/test_mpl_integration.py

@@ -8,7 +8,6 @@
 
 import numpy as np
 import matplotlib.pyplot as plt
-from packaging.version import parse as parse_version
 import pytest
 
 import cartopy.crs as ccrs
@@ -110,9 +109,7 @@ def test_global_scatter_wrap_no_transform():
 
 
 @pytest.mark.natural_earth
-@pytest.mark.mpl_image_compare(
-    filename='global_hexbin_wrap.png',
-    tolerance=2 if MPL_VERSION < parse_version('3.2') else 0.5)
+@pytest.mark.mpl_image_compare(filename='global_hexbin_wrap.png')
 def test_global_hexbin_wrap():
     ax = plt.axes(projection=ccrs.PlateCarree())
     ax.coastlines(zorder=2)
@@ -131,7 +128,7 @@ def test_global_hexbin_wrap():
 @pytest.mark.natural_earth
 @pytest.mark.mpl_image_compare(
     filename='global_hexbin_wrap.png',
-    tolerance=2 if MPL_VERSION < parse_version('3.2') else 0.5)
+    tolerance=0.5)
 def test_global_hexbin_wrap_transform():
     ax = plt.axes(projection=ccrs.PlateCarree())
     ax.coastlines(zorder=2)
@@ -191,8 +188,7 @@ def test_simple_global():
                  id='TransverseMercator'),
 ])
 @pytest.mark.mpl_image_compare(
-    tolerance=(2.61 if MPL_VERSION.release[:2] == (3, 1) else
-               0.97 if MPL_VERSION.release[:2] < (3, 5) else 0.5),
+    tolerance=0.97 if MPL_VERSION.release[:2] < (3, 5) else 0.5,
     style='mpl20')
 def test_global_map(proj):
     if isinstance(proj, tuple):
@@ -844,8 +840,7 @@ def test_barbs_1d_transformed():
 @pytest.mark.natural_earth
 @pytest.mark.mpl_image_compare(
     filename='streamplot.png', style='mpl20',
-    tolerance=(42 if MPL_VERSION.release[:2] < (3, 2) else
-               9.77 if MPL_VERSION.release[:2] < (3, 5) else 0.5))
+    tolerance=9.77 if MPL_VERSION.release[:2] < (3, 5) else 0.5)
 def test_streamplot():
     x = np.arange(-60, 42.5, 2.5)
     y = np.arange(30, 72.5, 2.5)