install_requires does not handle any software, just python packages required. Hugin is just some external software. You can list it as dependency, e.g. in a readme file and user should take care to install it themselves. You may use some install creator (like NSIS on Windows) that will create installer that will also download and install external dependencies. Eventually you can write a code to download and install Hugin yourself.
If you can't explain it to a six year old, you don't understand it yourself, Albert Einstein
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs