Please find attached a patch for the problem.
With this patch applied, libapache2-mod-python works with python 3.9.
diff --git a/lib/python/mod_python/apache.py b/lib/python/mod_python/apache.py
index 7748108..4e5c1d8 100644
--- a/lib/python/mod_python/apache.py
+++ b/lib/python/mod_python/apache.py
@@ -26,7 +26,7 @@ import pdb
import stat
import imp
import types
-import cgi
+import html
import _apache
try:
@@ -549,7 +549,7 @@ class CallBack:
s = '\n<pre>\nMod_python error: "%s %s"\n\n' % (phase,
hname)
for e in traceback.format_exception(etype, evalue, etb):
- s = s + cgi.escape(e) + '\n'
+ s = s + html.escape(e) + '\n'
s = s + "</pre>\n"
if filter:
diff --git a/lib/python/mod_python/psp.py b/lib/python/mod_python/psp.py
index f994847..cae778c 100644
--- a/lib/python/mod_python/psp.py
+++ b/lib/python/mod_python/psp.py
@@ -25,7 +25,7 @@ import sys
import os
import marshal
import types
-from cgi import escape
+from html import escape
import dbm, dbm
import tempfile
