Git Blame functionality already provided with a plugin currently installed

[grepsedawk]

The plugin vim-fugitive that you already have installed provides the same thing as your <Leader>b command with a little bit more extended functionality. The command is :GBlame and it also provides you with commit navigation.
If your current blame operation works and you like it, great. Otherwise, this plugin's git blame functionality is a little more feature rich than your current setup.

[grepsedawk]

This is the leader command I am referencing: https://github.com/r00k/dotfiles/blob/master/vimrc#L75