First, get the sources of yabgp:

$ git clone https://github.com/smartbgp/yabgp

Now to build yabgp:

$ cd yabgp

Install the requirements following this command, and observe the following logs:

$ pip install -r requirements.txt
..
Successfully installed Twisted Flask Flask-HTTPAuth netaddr zope.interface Werkzeug Jinja2 itsdangerous MarkupSafe
Cleaning up...

Now you may confirm the correct installation of yabgpd by using the following command:

$ cd bin
$ python yabgpd -h
  

This will output detailed help information on yabgpd.