Support CNTK installation in VirtualEnv

CNTK installation using pip place dlls in the root folder of the python environment. Unlike Conda, VirtualEnv doesn't add this folder in library search path and hence 'import CNTK' is broken in VirtualEnv. Fix: Place CNTK libraries in site-packages/CNTK/lib and add the same to library search path.

bindings/python/cntk/__init__.py

@@ -5,6 +5,9 @@
 
 __version__ = '2.3.1+'
 
+import os
+os.environ["PATH"] += os.pathsep + os.path.join(os.path.dirname(__file__), 'libs')
+
 import numpy as np
 
 from . import cntk_py

bindings/python/setup.py

@@ -159,15 +159,8 @@ cntk_module = Extension(
 packages = [x for x in find_packages() if x.startswith('cntk') and not x.startswith('cntk.swig')]
 
 package_data = { 'cntk': ['pytest.ini', 'io/tests/tf_data.txt', 'contrib/deeprl/tests/data/initial_policy_network.dnn'] }
-
-if IS_WINDOWS:
-    # On Windows copy all runtime libs to the base folder of Python
-    kwargs = dict(data_files = [('.', [ os.path.join('cntk', lib) for lib in rt_libs ])],
-                  package_data = package_data)
-else:
-    # On Linux copy all runtime libs into the cntk/lib folder.
-    package_data['cntk'] += rt_libs
-    kwargs = dict(package_data = package_data)
+package_data['cntk'] += rt_libs
+kwargs = dict(package_data = package_data)
 
 cntk_install_requires = [
     'numpy>=1.11',