PYTHONPATH set s.t. unit tests prefer compiled version

cmake_support/OST.cmake

@@ -702,9 +702,9 @@ macro(ost_unittest)
     foreach(py_test ${PY_TESTS})
       set(python_path $ENV{PYTHONPATH})
       if(python_path)
-        set(python_path "${python_path}:")
+        set(python_path ":${python_path}")
       endif(python_path)
-      set(python_path "${python_path}${LIB_STAGE_PATH}/python${PYTHON_VERSION}/site-packages")
+      set(python_path "${LIB_STAGE_PATH}/python${PYTHON_VERSION}/site-packages${python_path}")
       if(WIN32)
         set (PY_TESTS_CMD "PYTHONPATH=${python_path}  ${PYTHON_BINARY}")
         # todo fix python unit test running for Windows