What does “error: option --single-version-externally-managed not recognized” indicate?

Question

I seem to have suddenly started encounter the error error: option --single-version-externally-managed not recognized when pip installing varions pa

Answer 1

I have this problem on my macbook also when I try to upgrade one python package. I check pip version in OS X, it's too old: 1.1. I use follow cmd to upgrade pip to 1.5.6

easy_install -U pip

Then this error is fixed.