What is the meaning of the below statement incurred when invoking tlmgr install:
TLDownload::get_file: response error: 401 Sorry, the maximum number of allowed clients (10) are already connected. (for ftp://tug.org/historic/systems/texlive/2015/tlnet-final/archive/biblatex.tar.xz)
It gives an impression that there will be infinitely the maximum number of allowed clients connected and thus you will never be able to install your package.
By switching to another mirror, as suggested, I run into another problem related to checksum:
tlmgr --repository http://mirror.easyname.at/ctan/systems/texlive/tlnet install feynmf (running on Debian, switching to user mode!)
Unknown directive ...containerchecksum c59200574a316416a23695c258edf3a32531fbda43ccdc09360ee105c3f07f9fb77df17c4ba4c2ea4f3a5ea6667e064b51e3d8c2fe6c984ba3e71b4e32716955... , please fix it! at /usr/share/texlive/tlpkg/TeXLive/TLPOBJ.pm line 210, line 5579.
I reported this problem in another post