remove python 2.x specific urllib2's functions

IPython/core/display.py

@@ -516,10 +516,8 b' class DisplayObject(object):'
                 self.data = f.read()
         elif self.url is not None:
             try:
-                try:
-                    from urllib.request import urlopen  # Py3
-                except ImportError:
-                    from urllib2 import urlopen
+                # Deferred import
+                from urllib.request import urlopen
                 response = urlopen(self.url)
                 self.data = response.read()
                 # extract encoding from header, if there is one:

IPython/core/extensions.py

@@ -155,12 +155,8 b' class ExtensionManager(Configurable):'
             copy = copyfile
         else:
             # Deferred imports
-            try:
-                from urllib.parse import urlparse  # Py3
-                from urllib.request import urlretrieve
-            except ImportError:
-                from urlparse import urlparse
-                from urllib import urlretrieve
+            from urllib.parse import urlparse
+            from urllib.request import urlretrieve
             src_filename = urlparse(url).path.split('/')[-1]
             copy = urlretrieve
 

IPython/core/interactiveshell.py

@@ -3124,10 +3124,7 b' class InteractiveShell(SingletonConfigurable):'
         except UnicodeDecodeError:
             if not py_only :
                 # Deferred import
-                try:
-                    from urllib.request import urlopen  # Py3
-                except ImportError:
-                    from urllib import urlopen
+                from urllib.request import urlopen
                 response = urlopen(target)
                 return response.read().decode('latin1')
             raise ValueError(("'%s' seem to be unreadable.") % target)

IPython/lib/display.py

@@ -263,10 +263,9 b' class YouTubeVideo(IFrame):'
         super(YouTubeVideo, self).__init__(src, width, height, **kwargs)
     
     def _repr_jpeg_(self):
-        try:
-            from urllib.request import urlopen  # Py3
-        except ImportError:
-            from urllib2 import urlopen
+        # Deferred import
+        from urllib.request import urlopen
+
         try:
             return urlopen("https://img.youtube.com/vi/{id}/hqdefault.jpg".format(id=self.id)).read()
         except IOError: