cst/ducktape: Accept errors due to gap in manifest

The scrubber test may remove the first segment in the manifest. This
causes a difference between the manifest start offset and the first
segment start offset. The mismatch causes a validation to fail when
spillover is applied (which is correct behavior).

To avoid the test failing due to this expected set of events, the error
log is accepted in the test.

tests/rptest/tests/cloud_storage_scrubber_test.py

@@ -487,6 +487,9 @@ def _assert_segment_metadata_anomalies(
         # Remove the metadata for the penultimate segment, thus creating an offset gap
         # for the scrubber to detect
         found = False
+        seg_to_remove_name = None
+        seg_to_remove_meta = None
+        detect_at_seg_meta = None
         for crnt_seg, next_seg in itertools.pairwise(sorted_segments):
             name, meta = crnt_seg
 
@@ -507,11 +510,27 @@ def _assert_segment_metadata_anomalies(
                 found = True
                 break
 
-        assert found, f"Could not find a segment to remove from the STM manifest"
+        assert found, "Could not find a segment to remove from the STM manifest"
 
         self.logger.info(f"Removing segment with meta {seg_to_remove_meta}")
         self.logger.info(f"Anomaly should be detected at {detect_at_seg_meta}")
         manifest['segments'].pop(seg_to_remove_name)
+        """
+        The operation above may remove the first segment in the manifest. This
+        causes a difference between the manifest start offset and the first
+        segment start offset. The mismatch causes a validation to fail when
+        spillover is applied (which is correct behavior) by archival STM.
+
+        To avoid the test failing due to this expected set of events, the error
+        log is added to accept list here.
+        """
+        sorted_segments = sorted(manifest['segments'].items(),
+                                 key=lambda entry: entry[1]['base_offset'])
+        expect_error_at_offset = sorted_segments[0][1]['base_offset']
+        self.expected_error_logs.append(
+            re.compile(
+                fr"Can't apply spillover_cmd.*base_offset: {expect_error_at_offset}"
+            ))
 
         # Forcefully reset the manifest. Remote writes are disabled first
         # to make this operation safe.