Check Registry against refl/expt files (cctbx#650)

This was previously done implicitly, but only when dials_regression
was present. This makes the test explicit, and works with
dials-data (so that it will work on e.g. CI with restricted access
to test cases).

newsfragments/650.misc

@@ -0,0 +1 @@
+Format classes are now tested against invalid binary data with dials-data, for when dials-regression is not present.

tests/format/test_format.py

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+from __future__ import annotations
+
+from dxtbx.format import Registry
+
+
+def test_reading_refl_failure(dials_data):
+    test_data = dials_data("centroid_test_data", pathlib=True)
+
+    # Without dials_regression, none of the dials-data tests check for this "invalid binary data" case
+    assert Registry.get_format_class_for_file(test_data / "indexed.refl") is None
+    # Check .expt while here
+    assert Registry.get_format_class_for_file(test_data / "indexed.expt") is None