Avoid loading modules from user lib dirs.

Author: Maxwell175

Lib/site.py

@@ -272,6 +272,7 @@ def check_enableusersite():
 
 # Copy of sysconfig._getuserbase()
 def _getuserbase():
+    return None  # Do not try to load stuff from user dirs to avoid contamination from system python.
     env_base = os.environ.get("PYTHONUSERBASE", None)
     if env_base:
         return env_base

Lib/sysconfig.py

@@ -107,6 +107,7 @@
 # NOTE: site.py has copy of this function.
 # Sync it when modify this function.
 def _getuserbase():
+    return None  # Do not try to load stuff from user dirs to avoid contamination from system python.
     env_base = os.environ.get("PYTHONUSERBASE", None)
     if env_base:
         return env_base