Use full virtualenv for sysmon

This commit sets up a full virtualenv setup for chromite and uses the
full virtualenv for sysmon.

The full virtualenv includes chromite itself, which allows running
Python modules directly by import path without script path finding
code with half a dozen special cases.

Due to the repository layout, this requires a symlink to chromite
itself so pip can pull chromite into the virtualenv.

BUG=chromium:645611
TEST=Run sysmon

Change-Id: If0602eb02bcab58cda9c60d7225b3dfc53e2f2ac
Reviewed-on: https://chromium-review.googlesource.com/421273
Commit-Ready: Allen Li <ayatane@chromium.org>
Tested-by: Allen Li <ayatane@chromium.org>
Reviewed-by: Allen Li <ayatane@chromium.org>
diff --git a/scripts/virtualenv_wrapper_unittest.py b/scripts/virtualenv_wrapper_unittest.py
index ed82691..af07d91 100644
--- a/scripts/virtualenv_wrapper_unittest.py
+++ b/scripts/virtualenv_wrapper_unittest.py
@@ -12,12 +12,13 @@
 from chromite.scripts import virtualenv_wrapper
 
 _MODULE_DIR = os.path.dirname(os.path.realpath(__file__))
-_VENV_DIR = os.path.abspath(os.path.join(_MODULE_DIR, '..', '.venv'))
 
 
 class VirtualEnvTest(cros_test_lib.TestCase):
   """Test that we are running in a virtualenv."""
 
+  # pylint: disable=protected-access
+
 
   def testModuleIsFromVenv(self):
     """Test that we import |six| from the virtualenv."""
@@ -25,7 +26,7 @@
     # be provided inside the chromite virtualenv.
     six = __import__('six')
     req_path = os.path.dirname(os.path.realpath(six.__file__))
-    self.assertIn(_VENV_DIR, req_path)
+    self.assertIn(virtualenv_wrapper._VENV_DIR, req_path)
 
 
   def testInsideVenv(self):