Move constants

BUG=chromium:703769
TEST=None

Change-Id: I1c02a34009ed0d26c30d61f3e9a69e6817d5ef71
diff --git a/cros_venv/__init__.py b/cros_venv/__init__.py
index 72ddb66..07a8f31 100644
--- a/cros_venv/__init__.py
+++ b/cros_venv/__init__.py
@@ -14,8 +14,3 @@
 
     $ python2 -m unittest discover venv
 """
-
-import os
-
-PACKAGE_DIR = os.path.abspath(__path__[0])
-WORKTREE_DIR = os.path.dirname(PACKAGE_DIR)
diff --git a/cros_venv/constants.py b/cros_venv/constants.py
new file mode 100644
index 0000000..18cdb95
--- /dev/null
+++ b/cros_venv/constants.py
@@ -0,0 +1,27 @@
+# Copyright 2017 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""This package contains modules for creating and updating virtualenvs.
+
+To run:
+
+    $ python2 -m venv
+
+See __main__.py for details.
+
+To run the tests:
+
+    $ python2 -m unittest discover venv
+"""
+
+from __future__ import absolute_import
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import os
+
+import cros_venv
+
+PACKAGE_DIR = os.path.abspath(cros_venv.__path__[0])
+WORKTREE_DIR = os.path.dirname(PACKAGE_DIR)
diff --git a/cros_venv/venvlib.py b/cros_venv/venvlib.py
index 0da7c4e..bc2967a 100644
--- a/cros_venv/venvlib.py
+++ b/cros_venv/venvlib.py
@@ -14,10 +14,10 @@
 import subprocess
 import sys
 
-import cros_venv
+from cros_venv import constants
 from cros_venv import flock
 
-_PACKAGE_DIR = os.path.join(cros_venv.WORKTREE_DIR, 'pip_packages')
+_PACKAGE_DIR = os.path.join(constants.WORKTREE_DIR, 'pip_packages')
 _VENV_PY = '/usr/bin/python2.7'
 
 # BASE_DEPENDENCIES are pip requirements automatically included in every