Pillow was not correcty installed.
I had to do :
apt-get install libjpeg-dev
apt-get install zlib1g-dev
pip install --upgrade Pillow
To make it work.
But i still have this logs when i display an image
2017-11-14 19:22:43,500 [ERROR] seahub.thumbnail.views:77 latest_entry [Errno 2] No such file or directory: '/home/cc/seafile/seahub-data/thumbnail/thumb/1024/9d0dd60e7364fbdab56e894ad88bda4f9495a6db'
2017-11-14 19:22:43,500 [ERROR] seahub.thumbnail.views:77 latest_entry [Errno 2] No such file or directory: '/home/cc/seafile/seahub-data/thumbnail/thumb/1024/d22475bc9c5bed9327dd4bc2e9e6b00b9bb70f3f'
2017-11-14 19:22:43,543 [ERROR] seahub.thumbnail.views:77 latest_entry [Errno 2] No such file or directory: '/home/cc/seafile/seahub-data/thumbnail/thumb/1024/3a78519128e5258ba85b44a67c6d37bcc7a9e565'
2017-11-14 19:22:43,543 [ERROR] seahub.thumbnail.views:77 latest_entry [Errno 2] No such file or directory: '/home/cc/seafile/seahub-data/thumbnail/thumb/1024/cb29899383815ca3c3986a153a4de1c3255226dc'
Can anyone help ?
Regards