Homebrew errors; update fails
Solution 1:
The brew doctor should be helpful about this, next best thing to try is repairing formulae from taps with brew tap --repair. If that still does not help, try the following steps:
brew untap <X> where is from brew tap.
cd $(brew --prefix)
git clean -fd
git reset origin/master --force
brew update
brew tap <X> to have your taps again.