TST: Skip scipy tests if scipy isn't installed

Scipy isn't a required dependency, so skip the tests that require
scipy if scipy isn't found.

lib/cartopy/tests/mpl/test_contour.py

@@ -8,8 +8,13 @@
 import numpy as np
 from numpy.testing import assert_array_almost_equal
 import pytest
-from scipy.interpolate import NearestNDInterpolator
-from scipy.signal import convolve2d
+
+
+try:
+    from scipy.interpolate import NearestNDInterpolator
+    from scipy.signal import convolve2d
+except ImportError:
+    pytest.skip("scipy is required for contouring", allow_module_level=True)
 
 import cartopy.crs as ccrs
 

lib/cartopy/tests/mpl/test_mpl_integration.py

@@ -820,6 +820,8 @@ def test_quiver_rotated_pole():
 @pytest.mark.natural_earth
 @pytest.mark.mpl_image_compare(filename='quiver_regrid.png')
 def test_quiver_regrid():
+    # scipy required for regridding
+    pytest.importorskip("scipy")
     x = np.arange(-60, 42.5, 2.5)
     y = np.arange(30, 72.5, 2.5)
     x2d, y2d = np.meshgrid(x, y)
@@ -840,6 +842,8 @@ def test_quiver_regrid():
 @pytest.mark.mpl_image_compare(filename='quiver_regrid_with_extent.png',
                                tolerance=0.54)
 def test_quiver_regrid_with_extent():
+    # scipy required for regridding
+    pytest.importorskip("scipy")
     x = np.arange(-60, 42.5, 2.5)
     y = np.arange(30, 72.5, 2.5)
     x2d, y2d = np.meshgrid(x, y)
@@ -883,6 +887,8 @@ def test_barbs():
 @pytest.mark.natural_earth
 @pytest.mark.mpl_image_compare(filename='barbs_regrid.png')
 def test_barbs_regrid():
+    # scipy required for regridding
+    pytest.importorskip("scipy")
     x = np.arange(-60, 42.5, 2.5)
     y = np.arange(30, 72.5, 2.5)
     x2d, y2d = np.meshgrid(x, y)
@@ -903,6 +909,8 @@ def test_barbs_regrid():
 @pytest.mark.mpl_image_compare(filename='barbs_regrid_with_extent.png',
                                tolerance=0.54)
 def test_barbs_regrid_with_extent():
+    # scipy required for regridding
+    pytest.importorskip("scipy")
     x = np.arange(-60, 42.5, 2.5)
     y = np.arange(30, 72.5, 2.5)
     x2d, y2d = np.meshgrid(x, y)
@@ -958,6 +966,8 @@ def test_barbs_1d_transformed():
 @pytest.mark.natural_earth
 @pytest.mark.mpl_image_compare(filename='streamplot.png', style='mpl20')
 def test_streamplot():
+    # scipy required for regridding
+    pytest.importorskip("scipy")
     x = np.arange(-60, 42.5, 2.5)
     y = np.arange(30, 72.5, 2.5)
     x2d, y2d = np.meshgrid(x, y)

lib/cartopy/tests/test_img_transform.py

@@ -7,7 +7,13 @@
 import numpy as np
 from numpy.testing import assert_array_equal
 import pytest
-import scipy.spatial
+
+
+try:
+    import scipy.spatial
+except ImportError:
+    pytest.skip("scipy is required for image transforms", allow_module_level=True)
+
 
 import cartopy.crs as ccrs
 import cartopy.img_transform as img_trans

lib/cartopy/tests/test_vector_transform.py

@@ -6,6 +6,14 @@
 
 import numpy as np
 from numpy.testing import assert_array_almost_equal, assert_array_equal
+import pytest
+
+
+try:
+    import scipy  # noqa: F401
+except ImportError:
+    pytest.skip("scipy is required for vector transforms", allow_module_level=True)
+
 
 import cartopy.crs as ccrs
 import cartopy.vector_transform as vec_trans