Fix upload with old PyCURL
    
    To replicate the crash, use upload command with these versions:
    
     * GitPython-1.0.1-5.el7.noarch
     * python-pycurl-7.19.0-19.el7.x86_6
    
    Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>