hidden import needed for PyInstaller's binaries

an explicit 'import site' is needed for having a full functional interactive shell in the PyInstaller's binaries

gluon/shell.py

@@ -20,6 +20,7 @@ import logging
 import types
 import re
 import glob
+import site
 import traceback
 import gluon.fileutils as fileutils
 from gluon.settings import global_settings