Issue #19375: The site module adding a "site-python" directory to sys.path, if it exists, is now deprecated.

Doc/library/site.rst

@@ -38,6 +38,9 @@ Unix and Macintosh).  For each of the distinct head-tail combinations, it sees
 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.
 
+.. deprecated:: 3.4
+   Support for the "site-python" directory will be removed in 3.5.
+
 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

Doc/whatsnew/3.4.rst

@@ -685,7 +685,8 @@ Deprecated functions and types of the C API
 Deprecated features
 -------------------
 
-* No feature deprecations are planned for Python 3.4.
+* The site module adding a "site-python" directory to sys.path, if it
+  exists, is deprecated (:issue:`19375`).
 
 
 Porting to Python 3.4

Lib/site.py

@@ -326,6 +326,11 @@ def addsitepackages(known_paths, prefixes=None):
     """Add site-packages (and possibly site-python) to sys.path"""
     for sitedir in getsitepackages(prefixes):
         if os.path.isdir(sitedir):
+            if "site-python" in sitedir:
+                import warnings
+                warnings.warn('"site-python" directories will not be '
+                              'supported in 3.5 anymore',
+                              DeprecationWarning)
             addsitedir(sitedir, known_paths)
 
     return known_paths

Misc/NEWS

@@ -27,6 +27,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #19375: The site module adding a "site-python" directory to sys.path,
+  if it exists, is now deprecated.
+
 - Issue #19379: Lazily import linecache in the warnings module, to make
   startup with warnings faster until a warning gets printed.