--prepend option not prepending a file

[labs-stellios]

I've specified a file in an absolute directory, and still do not see any file prepended to my obfuscated output.

  pyminifier --obfuscate \
             --replacement-length=10 \
             --nonlatin \
             --prepend=/tmp/copyright_notice \
             ${new_file} > ${new_file}.obf

I've installed pyminifier-2.0 as:

install_obfuscator() {
  local package_name="pyminifier"
  local version="2.0"

  wget https://pypi.python.org/packages/source/${package_name:0:1}/${package_name}/${package_name}-${version}.tar.gz
  tar zxfv ${package_name}-${version}.tar.gz > /dev/null
  cd ${package_name}-${version}
  python3 setup.py install
}