'Could not import backend for traits' with Pyqt4 and mac os 10.10.5

So I tried many ways (pip, conda, easy_install, python setup develop source_code) to install mayavi, with pyqt4 and all other dependences (traits, traitsui, pyface, apptools, envisage) installed with conda, on mac os 10.10.5, but there is always an error that:
> (mayavi2) ➜ mayavi git:(master) ✗ mayavi2
Traceback (most recent call last):
File "/Users/penny/anaconda/envs/mayavi2/bin/mayavi2", line 6, in
sys.exit(main())
File "/Users/penny/anaconda/envs/mayavi2/lib/python2.7/site-packages/mayavi/scripts/mayavi2.py", line 646, in main
'''
ImportError: Could not import backend for traits
Make sure that you have either the TraitsBackendWx or the TraitsBackendQt
projects installed. If you installed Mayavi with easy_install, try easy_install
. easy_install Mayavi[app] will also work.

I tried to install `TraitsBackendQt` but there is no matching package on current osx-64 , any suggestions on making it work? Many thanks!