Fix #2733 -- allow only modern Jupyter versions

Signed-off-by: Chris Warrick <kwpolska@gmail.com>

CHANGES.txt

@@ -28,6 +28,12 @@ Bugfixes
 * Use page.tmpl by default, which is inherited from story.tmpl (Issue
   #1891)
 
+Other
+-----
+
+* Limit Jupyter support to notebook >= 4.0.0 (it already was in
+  requirements-extras.txt; Issue #2733)
+
 New in v7.8.5
 =============
 

nikola/plugins/compile/ipynb.py

@@ -39,27 +39,8 @@
     from jupyter_client import kernelspec
     from traitlets.config import Config
     flag = True
-    ipy_modern = True
 except ImportError:
-    try:
-        import IPython
-        from IPython.nbconvert.exporters import HTMLExporter
-        if IPython.version_info[0] >= 3:     # API changed with 3.0.0
-            from IPython import nbformat
-            current_nbformat = nbformat.current_nbformat
-            from IPython.kernel import kernelspec
-            ipy_modern = True
-        else:
-            import IPython.nbformat.current as nbformat
-            current_nbformat = 'json'
-            kernelspec = None
-            ipy_modern = False
-
-        from IPython.config import Config
-        flag = True
-    except ImportError:
-        flag = None
-        ipy_modern = None
+    flag = None
 
 from nikola import shortcodes as sc
 from nikola.plugin_categories import PageCompiler
@@ -81,8 +62,7 @@ def set_site(self, site):
 
     def _compile_string(self, nb_json):
         """Export notebooks as HTML strings."""
-        if flag is None:
-            req_missing(['ipython[notebook]>=2.0.0'], 'build this site (compile ipynb)')
+        self._req_missing_ipynb()
         c = Config(self.site.config['IPYNB_CONFIG'])
         c.update(get_default_jupyter_config())
         exportHtml = HTMLExporter(config=c)
@@ -93,6 +73,10 @@ def _compile_string(self, nb_json):
     def _nbformat_read(in_file):
         return nbformat.read(in_file, current_nbformat)
 
+    def _req_missing_ipynb(self):
+        if flag is None:
+            req_missing(['notebook>=4.0.0'], 'build this site (compile ipynb)')
+
     def compile_string(self, data, source_path=None, is_two_file=True, post=None, lang=None):
         """Compile notebooks into HTML strings."""
         new_data, shortcodes = sc.extract_shortcodes(data)
@@ -128,8 +112,7 @@ def read_metadata(self, post, file_metadata_regexp=None, unslugify_titles=False,
         As ipynb file support arbitrary metadata as json, the metadata used by Nikola
         will be assume to be in the 'nikola' subfield.
         """
-        if flag is None:
-            req_missing(['ipython[notebook]>=2.0.0'], 'build this site (compile ipynb)')
+        self._req_missing_ipynb()
         source = post.source_path
         with io.open(source, "r", encoding="utf8") as in_file:
             nb_json = nbformat.read(in_file, current_nbformat)
@@ -139,8 +122,7 @@ def read_metadata(self, post, file_metadata_regexp=None, unslugify_titles=False,
 
     def create_post(self, path, **kw):
         """Create a new post."""
-        if flag is None:
-            req_missing(['ipython[notebook]>=2.0.0'], 'build this site (compile ipynb)')
+        self._req_missing_ipynb()
         content = kw.pop('content', None)
         onefile = kw.pop('onefile', False)
         kernel = kw.pop('ipython_kernel', None)
@@ -157,12 +139,8 @@ def create_post(self, path, **kw):
             # imported .ipynb file, guaranteed to start with "{" because it’s JSON.
             nb = nbformat.reads(content, current_nbformat)
         else:
-            if ipy_modern:
-                nb = nbformat.v4.new_notebook()
-                nb["cells"] = [nbformat.v4.new_markdown_cell(content)]
-            else:
-                nb = nbformat.new_notebook()
-                nb["worksheets"] = [nbformat.new_worksheet(cells=[nbformat.new_text_cell('markdown', [content])])]
+            nb = nbformat.v4.new_notebook()
+            nb["cells"] = [nbformat.v4.new_markdown_cell(content)]
 
             if kernelspec is not None:
                 if kernel is None:
@@ -190,10 +168,7 @@ def create_post(self, path, **kw):
             nb["metadata"]["nikola"] = metadata
 
         with io.open(path, "w+", encoding="utf8") as fd:
-            if ipy_modern:
-                nbformat.write(nb, fd, 4)
-            else:
-                nbformat.write(nb, fd, 'ipynb')
+            nbformat.write(nb, fd, 4)
 
 
 def get_default_jupyter_config():