|   | 1 |  initial version  | 
It seems that the first problem you've encountered is due to unpacking the binary archive in the directory Téléchargement, which contains non-ascii characters. The solution is simply to move the archive to another location (e.g. your home directory) before unpacking it. More precisely, to install the latest stable version of SageMath under Ubuntu, follow these steps:
cd 
mv Téléchargements/sage-7.6-Ubuntu_16.04-x86_64.tar.bz2 .
bunzip2 sage-7.6-Ubuntu_16.04-x86_64.tar.bz2
tar xvf sage-7.6-Ubuntu_16.04-x86_64.tar
cd SageMath
./sage -n jupyter
|   | 2 |  No.2 Revision  | 
It seems that the first problem you've encountered is due to unpacking the binary archive in the directory Téléchargement, the name of which contains non-ascii characters. The solution is simply to move the archive to another location (e.g. your home directory) before unpacking it. More precisely, to install the latest stable version of SageMath under Ubuntu, follow these steps:type the following in a console:
cd 
mv Téléchargements/sage-7.6-Ubuntu_16.04-x86_64.tar.bz2 .
bunzip2 sage-7.6-Ubuntu_16.04-x86_64.tar.bz2
tar xvf sage-7.6-Ubuntu_16.04-x86_64.tar
cd SageMath
./sage -n jupyter
 Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.
 
                
                Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.