I ran into a couple of issues while building vim with python support (which I haven't needed until now). I have arch linux and python3 was symlinked to /usr/bin/python, the build script cached this and once I fixed the symlink to point to /usr/bin/python2 it was still giving an error. I manually fixed the check in the build script, compiled, but then the plugin didn't recognize +python/dyn so I had to rebuild without python3 support. It seems to be working now and I'm compiling ycm_core. Also, if you're going to be building vim anyway, --enable-rubyinterp and check out the command-t plugin.