Better error message when comparing images

Tests/helper.py

@@ -15,6 +15,9 @@
 
 from PIL import Image, ImageMath, features
 
+# overridden in conftest.py
+pytestconfig = {"option": {"verbose": 0}}
+
 logger = logging.getLogger(__name__)
 
 
@@ -87,15 +90,23 @@ def assert_image(im, mode, size, msg=None):
 def assert_image_equal(a, b, msg=None):
     assert a.mode == b.mode, msg or f"got mode {repr(a.mode)}, expected {repr(b.mode)}"
     assert a.size == b.size, msg or f"got size {repr(a.size)}, expected {repr(b.size)}"
-    if a.tobytes() != b.tobytes():
+
+    original_verbosity = pytestconfig.option.verbose
+    try:
+        # set pytest's verbosity to 0 so that it doesn't show the full bytes diff
+        pytestconfig.option.verbose = 0
+        assert a.tobytes() == b.tobytes(), msg or "got different content"
+    except AssertionError:
         if HAS_UPLOADER:
             try:
                 url = test_image_results.upload(a, b)
                 logger.error(f"Url for test images: {url}")
             except Exception:
                 pass
 
-        assert False, msg or "got different content"
+        raise
+    finally:
+        pytestconfig.option.verbose = original_verbosity
 
 
 def assert_image_equal_tofile(a, filename, msg=None, mode=None):

conftest.py

@@ -1 +1,12 @@
 pytest_plugins = ["Tests.helper"]
+
+
+def pytest_configure(config):
+    """
+    Keep a reference to pytest's configuration in our helper class.
+    This function is called by pytest each time the configuration is updated.
+    https://docs.pytest.org/en/latest/reference/reference.html#pytest.hookspec.pytest_configure
+    """
+    import Tests.helper
+
+    Tests.helper.pytestconfig = config