Also save the ENABLE_USER_SITE setting in the user_override.

setuptools/tests/contexts.py

@@ -3,6 +3,7 @@ import os
 import shutil
 import sys
 import contextlib
+import site
 
 from ..compat import StringIO
 
@@ -57,3 +58,12 @@ def quiet():
         new_stderr.seek(0)
         sys.stdout = old_stdout
         sys.stderr = old_stderr
+
+
+@contextlib.contextmanager
+def save_user_site_setting():
+    saved = site.ENABLE_USER_SITE
+    try:
+        yield saved
+    finally:
+        site.ENABLE_USER_SITE = saved

setuptools/tests/fixtures.py

@@ -13,4 +13,5 @@ def user_override():
         with mock.patch('site.USER_BASE', user_base):
             with contexts.tempdir() as user_site:
                 with mock.patch('site.USER_SITE', user_site):
-                    yield
+                    with contexts.save_user_site_setting():
+                        yield