Analyze dead links

[Janik von Rotz]

The followings links are reported as dead:

https://leanpub.com/s/4W-ob-YDw2LE2aSMyosCtA.pdf
https://leanpub.com/s/aQDRwmoOi940mX_EB6N7Yg.pdf
https://leanpub.com/s/lDl9ZV0QW7zaE4BpitXVig.pdf
https://leanpub.com/s/znHIFrvBAYRST5nFBiQU5g.pdf
https://leanpub.com/s/DQLESXQ69TlVFQ9ogjrFLw.pdf
https://poshtestgallery.com/

As their all are reachable, this requires further investigation ...

The recent change to use the -head param might be a source of trouble.