Fixes for nbconvert under Python 3

IPython/nbconvert/filters/strings.py

@@ -19,7 +19,10 b' templates.'
 import os
 import re
 import textwrap
-from urllib2 import quote
+try:
+    from urllib.parse import quote  # Py 3
+except ImportError:
+    from urllib2 import quote  # Py 2
 from xml.etree import ElementTree
 
 from IPython.core.interactiveshell import InteractiveShell

IPython/nbconvert/preprocessors/convertfigures.py

@@ -48,7 +48,7 b' class ConvertFiguresPreprocessor(Preprocessor):'
 
         # Loop through all of the datatypes of the outputs in the cell.
         for index, cell_out in enumerate(cell.get('outputs', [])):
-            for data_type, data in cell_out.items():
+            for data_type, data in list(cell_out.items()):
                 # this must run *before* extract outputs,
                 # so figure_name and filename do not exist
                 self._convert_figure(cell_out, resources, data_type, data)

IPython/nbconvert/preprocessors/revealhelp.py

@@ -12,11 +12,8 b''
 # Imports
 #-----------------------------------------------------------------------------
 
-import os
-import urllib2
-
 from .base import Preprocessor
-from IPython.utils.traitlets import Unicode, Bool
+from IPython.utils.traitlets import Unicode
 
 #-----------------------------------------------------------------------------
 # Classes and functions