bpo-34901: add isolated (-I) flag to sys.flags (GH-9708)


https://bugs.python.org/issue34901
(cherry picked from commit 656d52dbfde3223cd2a3525d652b6cccb02fa991)

Co-authored-by: Danish Prakash <grafitykoncept@gmail.com>
diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index 6e0097e..a04d957 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -325,6 +325,7 @@
    :const:`debug`                :option:`-d`
    :const:`inspect`              :option:`-i`
    :const:`interactive`          :option:`-i`
+   :const:`isolated`             :option:`-I`
    :const:`optimize`             :option:`-O` or :option:`-OO`
    :const:`dont_write_bytecode`  :option:`-B`
    :const:`no_user_site`         :option:`-s`
@@ -347,6 +348,9 @@
    .. versionchanged:: 3.3
       Removed obsolete ``division_warning`` attribute.
 
+   .. versionchanged:: 3.4
+      Added ``isolated`` attribute for :option:`-I` ``isolated`` flag.
+
    .. versionchanged:: 3.7
       Added ``dev_mode`` attribute for the new :option:`-X` ``dev`` flag
       and ``utf8_mode`` attribute for the new  :option:`-X` ``utf8`` flag.