I'm running Ubuntu and installed YouCompleteMe via vundle.
I'm having the same issues as in this thread Vim YouCompleteMe configuration in that youcompleteme seems to be working, but only autocompletes with only shows words in the current file - however, the solutions in there didn't work for me.
When I used run_tests.sh, it was telling me flake8 was missing, so I installed that, then it complained about nose so I installed that. Now I'm seeing the errors
ERROR: Failure: ImportError (No module named hamcrest) ERROR: Failure: ImportError (No module named mock) ERROR: Failure: ImportError (No module named mock)