Issue 15241: Improved site.py documentation relating to venvs.
diff --git a/Doc/library/site.rst b/Doc/library/site.rst
index 071706a..3bf8a99 100644
--- a/Doc/library/site.rst
+++ b/Doc/library/site.rst
@@ -38,6 +38,15 @@
if it refers to an existing directory, and if so, adds it to ``sys.path`` and
also inspects the newly added path for configuration files.
+If a file named "pyvenv.cfg" exists one directory above sys.executable,
+sys.prefix and sys.exec_prefix are set to that directory and
+it is also checked for site-packages and site-python (sys.base_prefix and
+sys.base_exec_prefix will always be the "real" prefixes of the Python
+installation). If "pyvenv.cfg" (a bootstrap configuration file) contains
+the key "include-system-site-packages" set to anything other than "false"
+(case-insensitive), the system-level prefixes will still also be
+searched for site-packages; otherwise they won't.
+
A path configuration file is a file whose name has the form :file:`{name}.pth`
and exists in one of the four directories mentioned above; its contents are
additional items (one per line) to be added to ``sys.path``. Non-existing items