解码器JPEG不可用（使用virtualenv）

Question

我得到这个错误，当系统试图下载jpeg文件。我想我尝试了所有可能的解决方案（我在互联网上找到的），我安装/卸载了PIL，然后用pip尝试了Pillow。然后添加如下symbolink链接：

sudo ln -s /usr/lib/x86_64-linux-gnu/libjpeg.so /usr/lib/libjpeg.so

只是说文件存在。当我卸载Pillow并再次尝试安装（在virtualenv中）时，会收到以下警告：

warning: no files found matching '*.yaml'
warning: no files found matching '*.bdf' under directory 'Images'
warning: no files found matching '*.fli' under directory 'Images'
warning: no files found matching '*.gif' under directory 'Images'
warning: no files found matching '*.icns' under directory 'Images'
warning: no files found matching '*.ico' under directory 'Images'
warning: no files found matching '*.jpg' under directory 'Images'
warning: no files found matching '*.pbm' under directory 'Images'
warning: no files found matching '*.pil' under directory 'Images'
warning: no files found matching '*.png' under directory 'Images'
warning: no files found matching '*.ppm' under directory 'Images'
warning: no files found matching '*.psd' under directory 'Images'
warning: no files found matching '*.tar' under directory 'Images'
warning: no files found matching '*.webp' under directory 'Images'
warning: no files found matching '*.xpm' under directory 'Images'
warning: no files found matching 'README' under directory 'Sane'
warning: no files found matching 'README' under directory 'Scripts'
warning: no files found matching '*.icm' under directory 'Tests'
warning: no files found matching '*.txt' under directory 'Tk'

我怎样才能解决这个问题？你知道吗

p.S.我在virtualenv上使用Debian squeez和python2.7。