* Also, test_plot cannot run in MacOS because of matplotlib & ipython's
  limit.
* Add missing dependency in setup.py.
* fix #2264

keep debugging

debug

When using system python, "pip install" needs root previlege. Using virtualenv to avoid this.

In the original util.cmake. enable_virtualenv.c is always regenerated when cmake files are changed, which leads to the relinking of all the targets depends on paddle_utils.

Change-Id: Ia29cd3d205e401dc3d04fbaf3cba2b01f2f4f0ca