adding support for virtualenvs, which don't support site.getsitepackages

src/cs50/cs50.py

@@ -4,8 +4,9 @@
 import re
 import sys
 
+from distutils.sysconfig import get_python_lib
 from os.path import abspath, join
-from site import getsitepackages, getusersitepackages
+from site import getusersitepackages
 from termcolor import cprint
 from traceback import extract_tb, format_list, format_exception_only
 
@@ -16,8 +17,9 @@ def excepthook(type, value, tb):
     and user-specific site-packages directory.
 
     https://stackoverflow.com/a/33042323/5156190
+    https://stackoverflow.com/a/122340/5156190
     """
-    packages = tuple(join(abspath(p), "") for p in getsitepackages() + [getusersitepackages()])
+    packages = tuple(join(abspath(p), "") for p in [get_python_lib(), getusersitepackages()])
     for entry in extract_tb(tb):
         fmt = format_list((entry,))
         if (entry[0].startswith(packages)):