patch 8.2.0068: crash when using Python 3 with "utf32" encoding

Problem:    Crash when using Python 3 with "utf32" encoding. (Dominique Pelle)
Solution:   Use "utf-8" whenever enc_utf8 is set. (closes #5423)
diff --git a/src/if_py_both.h b/src/if_py_both.h
index 0763c65..bdac3fc 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -19,7 +19,7 @@
 typedef int Py_ssize_t;  // Python 2.4 and earlier don't have this type.
 #endif
 
-#define ENC_OPT ((char *)p_enc)
+#define ENC_OPT (enc_utf8 ? "utf-8" : (char *)p_enc)
 #define DOPY_FUNC "_vim_pydo"
 
 static const char *vim_special_path = "_vim_path_";
diff --git a/src/testdir/test_python3.vim b/src/testdir/test_python3.vim
index 2853302..397299e 100644
--- a/src/testdir/test_python3.vim
+++ b/src/testdir/test_python3.vim
@@ -167,3 +167,10 @@
     call assert_match( '^Vim(.*):RuntimeError: TEST$', v:exception )
   endtry
 endfunc
+
+func Test_unicode()
+  " this crashed Vim once
+  set encoding=utf32
+  py3 print('hello')
+  set encoding=utf8
+endfunc
diff --git a/src/version.c b/src/version.c
index 432ae4d..1c7dbba 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    68,
+/**/
     67,
 /**/
     66,