diff -r b74897b69184 Lib/test/test_os.py
--- a/Lib/test/test_os.py	Wed Nov 02 20:33:07 2016 -0400
+++ b/Lib/test/test_os.py	Thu Nov 03 11:35:35 2016 +0100
@@ -55,7 +55,8 @@
     groups = []
 try:
     import pwd
-    all_users = [u.pw_uid for u in pwd.getpwall()]
+    all_users = ([u.pw_uid for u in pwd.getpwall()] if
+                        hasattr(pwd, 'getpwall') else [])
 except ImportError:
     all_users = []
 try:
@@ -1423,7 +1424,12 @@
                         break
                 os.closerange(3, 256)
             with open({TESTFN!r}, 'rb') as f:
-                os.dup2(f.fileno(), fd)
+                new_fd = f.fileno()
+                # Issue #26935: posix allows new_fd and fd to be equal but
+                # some libc implementations have dup2 return an error in this
+                # case.
+                if new_fd != fd:
+                    os.dup2(new_fd, fd)
                 sys.stdout.buffer.write(os.urandom(4))
                 sys.stdout.buffer.write(os.urandom(4))
             """.format(TESTFN=support.TESTFN)