GitPython version: 1.0.2
File: git/remote.py
Line: 646
OS: Ubuntu 14.04LTS

Passing a refspec to git fetch through a remote, as in
repo.remotes.origin.fetch("+refs/heads/*:refs/remotes/origin/*")
will raise an error if the remote has no fetch refspec defined in the config:

AssertionError: Remote '%s' has no refspec set.
You can set it as follows: 'git config --add "remote.origin.fetch +refs/heads/*:refs/heads/*"'.

Also, note that the error message is incorrectly formatted because the remote's name is replaced only in the second line of the message (a %s appears in the first line of the final message).

The _assert_refspec() method should not be called if one or more refspecs were given as arguments to fetch().