caches: the file backend should report damaged DB in case of failures.

rhodecode/lib/rc_cache/backends.py

@@ -182,7 +182,7 b' class FileNamespaceBackend(PickleSeriali'
     def get_store(self):
         return self.filename
 
-    def get(self, key):
+    def _dbm_get(self, key):
         with self._dbm_file(False) as dbm:
             if hasattr(dbm, 'get'):
                 value = dbm.get(key, NO_VALUE)
@@ -196,6 +196,13 b' class FileNamespaceBackend(PickleSeriali'
                 value = self._loads(value)
             return value
 
+    def get(self, key):
+        try:
+            return self._dbm_get(key)
+        except Exception:
+            log.error('Failed to fetch DBM key %s from DB: %s', key, self.get_store())
+            raise
+
     def set(self, key, value):
         with self._dbm_file(True) as dbm:
             dbm[key] = self._dumps(value)