Don't simply quit on bad CRC?

[mxmlnkn]

In order to read from faulty media it might be helpful to not just "crash" with an exception when a bad crc is encountered.
I did simply quit because when a crc is wrong, I can't be sure anymore that the next bits are for the next block.
However, for the parallel version I added a blockfinder function, which can search for the magic bit strings of bzip2 blocks.
I could use that to recover from bad blocks.
Ironically, this is not the only new feature which I could get out of the box from the parallelized design.

How to do error reporting then, a simple message to stderr?