ColumnFamilyStore store = Table.open(cfm.tableName).getColumnFamilyStore(cfm.cfName);
assert store != null;
store.forceBlockingFlush();
assert DefsTable.getFiles(cfm.tableName, cfm.cfName).size() > 0;
new DropKeyspace(ks.name, true).apply();
assert DatabaseDescriptor.getTableDefinition(ks.name) == null;
// write should fail.
rm = new RowMutation(ks.name, dk.key);