Use FilterLabel in raw file tests.

These tests specifically require the physical filter, but changes in
afw mean that Filter.getName() only returns the physical filter if
there are no other names for it.

python/lsst/obs/base/butler_tests.py

@@ -143,7 +143,11 @@ def _test_exposure(self, name):
         self.assertEqual(exp.getDetector().getId(), self.butler_get_data.detectorIds[name])
         self.assertEqual(exp.getDetector().getName(), self.butler_get_data.detector_names[name])
         self.assertEqual(exp.getDetector().getSerial(), self.butler_get_data.detector_serials[name])
-        self.assertEqual(exp.getFilter().getName(), self.butler_get_data.filters[name])
+        # obs_test does not have physical filters, so include a fallback
+        exposureFilter = exp.getFilterLabel()
+        filterName = exposureFilter.physicalLabel if exposureFilter.hasPhysicalLabel() \
+            else exposureFilter.bandLabel
+        self.assertEqual(filterName, self.butler_get_data.filters[name])
         exposureId = self.butler.get('ccdExposureId', dataId=self.dataIds[name])
         self.assertEqual(exposureId, self.butler_get_data.exposureIds[name])
         self.assertEqual(exp.getInfo().getVisitInfo().getExposureTime(), self.butler_get_data.exptimes[name])