Visudo Gives no Error but asks "What Now?"

There is an error in the file you just edited, this is why visudo is complaining. From http://www.courtesan.com/sudo/man/1.7.10/visudo.man.html:

visudo parses the sudoers file after the edit and will not save the changes if there is a syntax error. Upon finding an error, visudo will print a message stating the line number(s) where the error occurred and the user will receive the “What now?” prompt. At this point the user may enter ‘e’ to re-edit the sudoers file, ‘x’ to exit without saving the changes, or ‘Q’ to quit and save changes. The ‘Q’ option should be used with extreme care because if visudo believes there to be a parse error, so will sudo and no one will be able to sudo again until the error is fixed. If ‘e’ is typed to edit the sudoers file after a parse error has been detected, the cursor will be placed on the line where the error occurred (if the editor supports this feature).

About your error, isn't the "python" command missing the complete path? I mean:

matt    ALL=(root) NOPASSWD: /usr/bin/python /home/matt/token-abe/setup.py install --force