fix backward `f, nb` args for nbformat.write

IPython/html/nbconvert/tests/test_nbconvert_handlers.py

@@ -67,7 +67,7 @@ class APITest(NotebookTestBase):
         
         with io.open(pjoin(nbdir, 'foo', 'testnb.ipynb'), 'w',
                      encoding='utf-8') as f:
-            write(f, nb, version=4)
+            write(nb, f, version=4)
 
         self.nbconvert_api = NbconvertAPI(self.base_url())
 

IPython/html/services/contents/filemanager.py

@@ -303,7 +303,7 @@ class FileContentsManager(ContentsManager):
             nb['metadata']['name'] = u''
 
         with atomic_writing(os_path, encoding='utf-8') as f:
-            nbformat.write(f, nb, version=nbformat.NO_CONVERT)
+            nbformat.write(nb, f, version=nbformat.NO_CONVERT)
 
     def _save_file(self, os_path, model, name='', path=''):
         """save a non-notebook file"""

IPython/html/services/contents/tests/test_contents_api.py

@@ -144,7 +144,7 @@ class APITest(NotebookTestBase):
             with io.open(pjoin(nbdir, d, '%s.ipynb' % name), 'w',
                          encoding='utf-8') as f:
                 nb = new_notebook()
-                write(f, nb, version=4)
+                write(nb, f, version=4)
 
             # create a text file
             with io.open(pjoin(nbdir, d, '%s.txt' % name), 'w',

IPython/html/services/sessions/tests/test_sessions_api.py

@@ -64,7 +64,7 @@ class SessionAPITest(NotebookTestBase):
         with io.open(pjoin(nbdir, 'foo', 'nb1.ipynb'), 'w',
                      encoding='utf-8') as f:
             nb = new_notebook()
-            write(f, nb, version=4)
+            write(nb, f, version=4)
 
         self.sess_api = SessionAPI(self.base_url())
 

IPython/html/tests/test_files.py

@@ -74,7 +74,7 @@ class FilesTest(NotebookTestBase):
 
         with io.open(pjoin(nbdir, 'testnb.ipynb'), 'w', 
             encoding='utf-8') as f:
-            write(f, nb, version=4)
+            write(nb, f, version=4)
 
         with io.open(pjoin(nbdir, 'test.bin'), 'wb') as f:
             f.write(b'\xff' + os.urandom(5))