Fix Python 3 handling of urllib

Added try/except blocks to properly import moved methods in the
urllib and urllib2 modules. This would break things including `%load`ing
scripts by url and installing a local copy of MathJax.

IPython/core/display.py

@@ -312,8 +312,11 b' class DisplayObject(object):'
                 self.data = f.read()
         elif self.url is not None:
             try:
-                import urllib2
-                response = urllib2.urlopen(self.url)
+                try:
+                    from urllib.request import urlopen  # Py3
+                except ImportError:
+                    from urllib2 import urlopen
+                response = urlopen(self.url)
                 self.data = response.read()
                 # extract encoding from header, if there is one:
                 encoding = None

IPython/core/extensions.py

@@ -169,11 +169,13 b' class ExtensionManager(Configurable):'
             src_filename = os.path.basename(url)
             copy = copyfile
         else:
-            from urllib import urlretrieve  # Deferred imports
+            # Deferred imports
             try:
                 from urllib.parse import urlparse  # Py3
+                from urllib.request import urlretrieve
             except ImportError:
                 from urlparse import urlparse
+                from urllib import urlretrieve
             src_filename = urlparse(url).path.split('/')[-1]
             copy = urlretrieve
             

IPython/core/interactiveshell.py

@@ -3088,7 +3088,11 b' class InteractiveShell(SingletonConfigurable):'
                 return openpy.read_py_url(utarget, skip_encoding_cookie=skip_encoding_cookie)
         except UnicodeDecodeError:
             if not py_only :
-                from urllib import urlopen  # Deferred import
+                # Deferred import
+                try:
+                    from urllib.request import urlopen  # Py3
+                except ImportError:
+                    from urllib import urlopen
                 response = urlopen(target)
                 return response.read().decode('latin1')
             raise ValueError(("'%s' seem to be unreadable.") % utarget)

IPython/core/magics/code.py

@@ -235,7 +235,11 b' class CodeMagics(Magics):'
             print(e.args[0])
             return
 
-        from urllib2 import urlopen  # Deferred import
+        # Deferred import
+        try:
+            from urllib.request import urlopen # Py 3
+        except ImportError:
+            from urllib2 import urlopen
         import json
         post_data = json.dumps({
           "description": opts.get('d', "Pasted from IPython"),

IPython/external/mathjax.py

@@ -58,11 +58,15 b' import os'
 import shutil
 import sys
 import tarfile
-import urllib2
 import zipfile
 
 from IPython.utils.path import get_ipython_dir
 
+try:
+    from urllib.request import urlopen # Py 3
+except ImportError:
+    from urllib2 import urlopen
+
 #-----------------------------------------------------------------------------
 #
 #-----------------------------------------------------------------------------
@@ -167,7 +171,7 b" def install_mathjax(tag='v2.2', dest=default_dest, replace=False, file=None, ext"
         # download mathjax
         mathjax_url = "https://github.com/mathjax/MathJax/archive/%s.tar.gz" %tag
         print("Downloading mathjax source from %s" % mathjax_url)
-        response = urllib2.urlopen(mathjax_url)
+        response = urlopen(mathjax_url)
         file = response.fp
 
     print("Extracting to %s" % dest)

IPython/lib/display.py

@@ -183,6 +183,9 b' class IFrame(object):'
     def _repr_html_(self):
         """return the embed iframe"""
         if self.params:
+            try:
+                from urllib.parse import urlencode # Py 3
+            except ImportError:
             from urllib import urlencode
             params = "?" + urlencode(self.params)
         else:

IPython/utils/openpy.py

@@ -207,7 +207,11 b" def read_py_url(url, errors='replace', skip_encoding_cookie=True):"
     -------
     A unicode string containing the contents of the file.
     """
-    from urllib import urlopen  # Deferred import for faster start
+    # Deferred import for faster start
+    try:
+        from urllib.request import urlopen # Py 3
+    except ImportError:
+        from urllib import urlopen
     response = urlopen(url)
     buffer = io.BytesIO(response.read())
     return source_to_unicode(buffer, errors, skip_encoding_cookie)