[3.11] More actionable error message when spawn is incorrectly used. (G…

…H-102203) (#107991)

More actionable error message when spawn is incorrectly used. (GH-102203)
(cherry picked from commit a794ebe)

Co-authored-by: Yuxin Wu <ppwwyyxxc@gmail.com>
Co-authored-by: Yuxin Wu <ppwwyyxx@users.noreply.github.com>
Co-authored-by: Oleg Iarygin <oleg@arhadthedev.net>

Lib/multiprocessing/spawn.py

@@ -150,7 +150,11 @@ def _check_not_importing_main():
                 ...
 
         The "freeze_support()" line can be omitted if the program
-        is not going to be frozen to produce an executable.''')
+        is not going to be frozen to produce an executable.
+
+        To fix this issue, refer to the "Safe importing of main module"
+        section in https://docs.python.org/3/library/multiprocessing.html
+        ''')
 
 
 def get_preparation_data(name):