Handle open with TMPFILE flag

- added basic test for TemporaryFile
- fixes #509
- back-ported from master

CHANGES.md

@@ -7,8 +7,13 @@ _Note:_ pyfakefs 4.0 is planned for release at the end of 2019 or the beginning
 of 2020. As pyfakefs 4.0 is a major release, we are giving you advance notice of
 the proposed changes so you can be ready.
 
-  * pyfakefs 4.0 drops support for Python 2.7. If you still need
-    Python 2.7, you can continue to use the latest pyfakefs 3.x version. 
+## [Version 3.7.2](https://pypi.python.org/pypi/pyfakefs/3.7.2)
+
+This version backports some fixes from master.
+
+#### Fixes
+  * Fixed handling of `os.TMPFILE` flag under Linux
+    (see [#509](../../issues/509))
 
 ## [Version 3.7.1](https://pypi.python.org/pypi/pyfakefs/3.7.1)
 

pyfakefs/fake_filesystem.py

@@ -3726,8 +3726,10 @@ def open(self, path, flags, mode=None, dir_fd=None):
             else:
                 mode = 0o777 & ~self._umask()
 
+        has_tmpfile_flag = (hasattr(os, 'O_TMPFILE') and
+                            flags & getattr(os, 'O_TMPFILE'))
         open_modes = _OpenModes(
-            must_exist=not flags & os.O_CREAT,
+            must_exist=not flags & os.O_CREAT and not has_tmpfile_flag,
             can_read=not flags & os.O_WRONLY,
             can_write=flags & (os.O_RDWR | os.O_WRONLY),
             truncate=flags & os.O_TRUNC,

pyfakefs/tests/fake_tempfile_test.py

@@ -98,6 +98,12 @@ def test_temporary_directory(self):
             self.assertEqual(self.fs.get_object(tmpdir).st_mode,
                              stat.S_IFDIR | 0o700)
 
+    def test_temporary_file(self):
+        with tempfile.TemporaryFile() as f:
+            f.write(b'test')
+            f.seek(0)
+            self.assertEqual(b'test', f.read())
+
 
 if __name__ == '__main__':
     unittest.main()