Use sniff_prefix in bref3 datatype

lib/galaxy/datatypes/binary.py

@@ -245,24 +245,8 @@ class Bref3(Binary):
         super().__init__(**kwd)
         self._magic = binascii.unhexlify("7a8874f400156272")
 
-    def sniff(self, filename):
-        """
-        Try to guess if the file is a bref3 file.
-        >>> from galaxy.datatypes.sniff import get_test_fname
-        >>> fname = get_test_fname('affy_v_agcc.cel')
-        >>> Bref3().sniff(fname)
-        False
-        >>> fname = get_test_fname('ref.bref3')
-        >>> Bref3().sniff(fname)
-        True
-        """
-        try:
-            header = open(filename, 'rb').read(8)
-            if header == self._magic:
-                return True
-            return False
-        except Exception:
-            return False
+    def sniff_prefix(self, sniff_prefix):
+        return sniff_prefix.startswith_bytes(self._magic)
 
     def set_peek(self, dataset, is_multi_byte=False):
         if not dataset.dataset.purged: