# HG changeset patch
# Parent  d1c11a78b43a7a56a7c68211306ca5964afdcadf
Issue #25583: Avoid incorrect errors raised by os.makedirs(exist_ok=True)

diff -r d1c11a78b43a Lib/os.py
--- a/Lib/os.py	Tue Nov 10 19:52:20 2015 +0200
+++ b/Lib/os.py	Fri Nov 13 02:25:45 2015 +0000
@@ -230,7 +230,7 @@
         try:
             makedirs(head, mode, exist_ok)
         except FileExistsError:
-            # be happy if someone already created the path
+            # Defeats race condition when another thread created the path
             pass
         cdir = curdir
         if isinstance(tail, bytes):
@@ -239,8 +239,10 @@
             return
     try:
         mkdir(name, mode)
-    except OSError as e:
-        if not exist_ok or e.errno != errno.EEXIST or not path.isdir(name):
+    except OSError:
+        # Cannot rely on checking for EEXIST, since the operating system
+        # could give priority to other errors like EACCES or EROFS
+        if not exist_ok or not path.isdir(name):
             raise
 
 def removedirs(name):
diff -r d1c11a78b43a Lib/test/test_os.py
--- a/Lib/test/test_os.py	Tue Nov 10 19:52:20 2015 +0200
+++ b/Lib/test/test_os.py	Fri Nov 13 02:25:45 2015 +0000
@@ -1039,6 +1039,9 @@
         os.makedirs(path, mode=mode, exist_ok=True)
         os.umask(old_mask)
 
+        # Issue #25583: A drive root could raise PermissionError on Windows
+        os.makedirs(os.path.abspath('/'), exist_ok=True)
+
     def test_exist_ok_s_isgid_directory(self):
         path = os.path.join(support.TESTFN, 'dir1')
         S_ISGID = stat.S_ISGID
diff -r d1c11a78b43a Misc/NEWS
--- a/Misc/NEWS	Tue Nov 10 19:52:20 2015 +0200
+++ b/Misc/NEWS	Fri Nov 13 02:25:45 2015 +0000
@@ -79,6 +79,9 @@
 Library
 -------
 
+- Issue #25583: Avoid incorrect errors raised by os.makedirs(exist_ok=True)
+  when the OS gives priority to errors such as EACCES over EEXIST.
+
 - Issue #25584: Added "escape" to the __all__ list in the glob module.
 
 - Issue #25584: Fixed recursive glob() with patterns starting with '\*\*'.