Ignore arch specific cast warnings in tests (#7393)

Apparently astype(...) raises a warning on some platforms despite
`casting="unsafe"` being the default. I couldn't reproduce this as I
don't have access to the architectures this fails for [1, 2], but these
warnings should be harmless to ignore for these tests.

[1] https://www.github.com/scikit-image/scikit-image/issues/7391
[2] https://buildd.debian.org/status/logs.php?pkg=skimage&ver=0.23.1-1&suite=sid

skimage/filters/tests/test_unsharp_mask.py

@@ -1,3 +1,5 @@
+import warnings
+
 import numpy as np
 import pytest
 
@@ -38,7 +40,17 @@ def test_unsharp_masking_output_type_and_shape(
     radius, amount, shape, multichannel, dtype, offset, preserve
 ):
     array = np.random.random(shape)
-    array = ((array + offset) * 128).astype(dtype)
+    array = (array + offset) * 128
+    with warnings.catch_warnings():
+        # Ignore arch specific warning on arm64, armhf, ppc64el, riscv64, s390x
+        # https://github.com/scikit-image/scikit-image/issues/7391
+        warnings.filterwarnings(
+            action="ignore",
+            category=RuntimeWarning,
+            message="invalid value encountered in cast",
+        )
+        array = array.astype(dtype)
+
     if (preserve is False) and (dtype in [np.float32, np.float64]):
         array /= max(np.abs(array).max(), 1.0)
     channel_axis = -1 if multichannel else None

skimage/transform/tests/test_pyramids.py

@@ -1,4 +1,5 @@
 import math
+import warnings
 
 import pytest
 import numpy as np
@@ -194,8 +195,16 @@ def test_check_factor():
     'pyramid_func', [pyramids.pyramid_gaussian, pyramids.pyramid_laplacian]
 )
 def test_pyramid_dtype_support(pyramid_func, dtype):
-    img = np.random.randn(32, 8).astype(dtype)
-    pyramid = pyramid_func(img)
+    with warnings.catch_warnings():
+        # Ignore arch specific warning on arm64, armhf, ppc64el, riscv64, s390x
+        # https://github.com/scikit-image/scikit-image/issues/7391
+        warnings.filterwarnings(
+            action="ignore",
+            category=RuntimeWarning,
+            message="invalid value encountered in cast",
+        )
+        img = np.random.randn(32, 8).astype(dtype)
 
+    pyramid = pyramid_func(img)
     float_dtype = _supported_float_type(dtype)
     assert np.all([im.dtype == float_dtype for im in pyramid])