Comment 2 for bug 1286274

If anyone else experiences the same problem before the installer is fixed: you can work around it by downloading the installer file, applying the patch, and executing the local copy of the installer:

$ wget https://github.com/kovidgoyal/calibre/raw/master/setup/linux-installer.py
$ wget https://bugs.launchpad.net/calibre/+bug/1286274/+attachment/4001048/+files/proxy_debug.patch
$ patch < proxy_debug.patch
$ cat linux-installer.py | | sudo python -c "import sys; main=lambda:sys.stderr.write('Download failed\n'); exec(sys.stdin.read()); main()"